Cave Johnson.. Love J.K Simmons work overall but Cave was perfect.

Some of my favorites:

• GLaDOS from Portal 1+2: Ellen McClain did such a fantastic job balancing a monotonous robotic tone with human emotions and adding subtle glitches to show not everything was 100% alright. She defined what a female robot voice should sound like for that decade. I saw that Stephen Merchant was mentioned and while his performance was good and Wheatley's character was hilarious, I think McLain's performance as GLaDOS was more original and memorable.
• Narrator from The Stanley Parable: Kevan Brighting was arguably the protagonist of the game and the player was the annoying mob to him. As the only chacter with dialogue in the entire walking sim game, he had to carry almost the entire game's story, personality, and charm all through his voice. And it's honestly so fun how disappointed, annoyed, and exasperated he gets when the player refuses to listen.
• The Joker from Batman Arkham Asylum: This one is cheating cause Mark Hamill has played The Joker in almost every modern animated medium available. Still, there's a reason his version is so iconic. It's just so bittersweet that he refuses to ever voice The Joker again since Kevin Conroy, the VA for his Batman passed away.

Edit: After reviewing my list, it seems like I like offscreen narrators who insult the player. How funny

How has Baldur's Gate 3 not been mentioned in this thread yet? Huge cast and everyone is going for it. Even the narrator. Especially the narrator.

The whole cast of Team Fortress 2.

I haven't played that game in over a decade, yet if I read any of the lines from the game, I'll still hear their voices loud as day. Even just seeing the word "medic" and I hear Demoman screaming it.

Arthur Morgan in Red Dead 2

The narrator in The Stanley Parable made me lose it so many times.

Vaas from Far Cry 3.

This scene is always such a treat: https://youtu.be/rKMMCPeiQoc

Also Alan Tudyk Stephen Merchant in Portal 2.

Edit: Was just recently watching something with Alan in it and got them mixed up 😅

Stephen Merchant and JK Simmons do a great job in Portal 2

Dionysus in hades. Dude amps me up so well I pick him over boons I like better.

One of the best villains I can remember from a game, Handsome Jack in Borderlands 2. Maybe he was just written so well, but he was amazing.

Narrator in Bastion. Just glorious.

Leonard Nimoy - Civilization 4

https://www.youtube.com/watch?v=uE7uiKsfpVE

The first new Wolfenstein was amazing. They got actual German actors to play the nazis and it made a huge difference.

I think Hades is the best overall, which has been mentioned here. Everything from Supergiant Games is great. I've seen Disco Elysium mentioned too, which is also great.

But I think one game that is underappreciated and not mentioned here is Horizon: Zero Dawn. Ashley Burch won several awards for her performance as Aloy. I think part of the reason it gets forgotten is that the facial animations in cutscenes are bad, at least in the main game, which led to people just not liking the cutscenes very much. The DLC's animations are pretty good though.

Troy Baker & Ashley Johnson in Last of Us will stay with me for life.

Recency bias because I'm currently playing it, but Cherami Leigh, Keanu Reeves, and Idris Elba — and a ton of others — in Cyberpunk 2077. If you like sci-fi and fantasy, you're covered. Asuna from Sword Art Online. Neo from The Matrix. And Roland from The Dark Tower. The fact that the latter two actors have their characters modeled after them make it more than just voice acting, though. Johnny Silverhand moves like Keanu Reeves in addition to looking like him. And Solomon Reed moves like Idris Elba. That hulking walk he did in Luther? It's all over the Reed character. As for Cherami Leigh, well, you can make V look like whatever you want. You can even make her male, in whole or in part (trans/non-binary characters are possible, they even have a male voice actor).

I'm seeing a ton of great answers in the comments though. Shout-out to the person who said Portal. Ellen McLain has a role in Cyberpunk as well. Early on, in your garage, your car is struck by a robotaxi. The robotaxi's AI owner invites you to come to their facility for a tour as well as repayment as a way of apology, and he also has a mission for you. This AI has "children" that have been acting crazy (and, one of them hit your car) and he wants you to bring them back in. One of them is voiced by Ellen McLain. In her GLaDOS voice and with lines from Portal. It's amazing. They had to have gotten permission from Valve for that little stunt. If you like Portal, it's probably gonna be one of your favorite parts of Cyberpunk.

The only two I can think of that haven't been mentioned yet, but I feel must:

Disco Elysium

Skywind

The latter is unreleased, but pretty much all the voice acting is done and the work I've heard is impeccable.

Bastion, Hades. Basically all supergiantgames.

Legacy of Kain: Soul Reaver, for the original PlayStation. All these years later it’s still an amazing standout.

Whoever did the scientist's "ACK!" sound from Half Life 1.

Disco Elysium

Stay a while and listen...

Vampire the masquerade: Bloodlines has amazing voice acting, it's god-tier. Check out the character Fat-Larry😉

I really appreciate Commander Shepard (whoever the male is) when you select renegade options only. The voice lets out stoic, brazen, unfiltered bullshit that somehow fits in with everything going on. It's like the serious version of Zapp Brannigan. I wouldn't be surprised if Seth Green (Joker) influenced it and how to deliver it.

Also, John Marsden in RDR1. If you're not American and know little about their Wild West era, that voice delivery is such a big layer of immersion, whereas other voice acting can really disconnect you from the experience. It being the voice of you helps with feeling like a part of the world. Like compare that to the cowboy from Octopath 🤢

I also really enjoyed a lot of the voices from KCD2. Rosa and Hans are excellent.

I don't remember the actors names but here are characters and the games whose voice acting left an impression on me:

• Alistair and Morrigan from Dragon Age Origins
• Both leads from Firewatch
• Lee from Telltale's Walking Dead Season 1
• Most of the main characters from Red Dead Redemption 1 and 2
• The voices from Hellblade Senua's Sacrifice
• Astarion from Baldurs Gate 3 was head and shoulders above the rest, although the narrator was also very good
• Troy Baker knocked it out of the park as Indians Jones in the great circle
• All of the Uncharted games have fantastic voice acting. Nolan North was born to play Nathan Drake
• Similarly, the voice acting in The Last of Us is fantastic
• In the mass effect OT, special callout to Jennifer Hlae and Mark Meer (the latter especially grew into the role in the second and third game) and also to the actors who voices Garrus and Tali.

Half Life : Alyx. Everyone is great but I especially enjoyed Rhys Darby as the guy in your headset. Tony Todd as the Vortigaunts was also really good.

I've always loved the narrator of Darkest Dungeon, I just wish i didn't such at the game so bad.

I quite like the work in Max Payne, whoever did it.

Homeworld - Few lines. All brilliant. " Detecting no communication from anywhere in the system, not even beacons." - "We are being overwhelmed!"

Ixion - So many lines that would make no sense if they weren't being delivered with conviction and sincerity.

Every single line in the Soul Reaver trilogy is a masterpiece.

Here, see for yourself. The intro alone will pull you in and never let go.

It's gotta be the Obra Dinn for me, the vocals are such a huge part of the story and dine really well.

The special zombies in left 4 dead 1 & 2

I know it's super obscure, but there are some YouTube videos compiling each special zombie and it's like god tier sound. I bet they had fun doing it, too.

To this day, I still hype myself up to do weird sounds by listening to those because they're so good.

While Assassin's Creed: Odyssey is a bit of a mixed bag overall, Melissanthi Mahut as Kassandra will always be one of my favorites. Also Courtenay Taylor as female player character in Fallout 4, and Ashley Burch as Pavarti in Outer Worlds.

I gotta say David Hayter was the first video game voice actor I ever heard of and that’s because of a metal gear solid. I still think solid snake is my favourite game voice acting. Especially if you look at the subtle difference in Snake’s voice depending on the game. It was a complete travesty to have snake voiced by anyone else in 5, but in canon it makes sense i guess

It doesn't get better than JC Denton in Deus Ex.

Fight me.

Clair Obscur: Expedition 33

The voice actors really hit it out of the park with this one. But this scene in particular:

https://www.youtube.com/watch?v=7RQDMWXEJbE

The narrator in Indika. Or really anybody in Indika. Especially considering the English actors aren't even the original actors.

CURSE YOU BAYLE! I HEREBY VOW YOU WILL RUE THIS DAY! BEHOLD, A TRUE DRAKE WARRIOR, AND I, IGON! YOUR FEARS MADE FLESH! SOLID OF SCALE YOU MIGHT BE, FOUL DRAGON, BUT I WILL RIDDLE WITH HOLES YOUR ROTTEN HIDE! WITH A HAIL OF HARPOONS, WITH EVERY LAST DROP OF MY BEING!

Cpt. Janeway as Flemeth in the Dragon Age series (especially Origins).

Disco elysium, any supergiant game (hades/bastion) logan cunningham my beloved, legacy of kain, parts of mass effect, bad company 2

Jennifer Hale as FemShep in the Mass Effect series 1-3.

Final Fantasy 3/6. Kefka's laugh will forever be the best evil laugh.

I don't know if it is the best, but I liked the voice acting in Slay the Princess.

The voice acting in Hellblade always gives me chills.

The original Resident Evil

Deep Rock galactic has some of my favourite voices and lines in it.

In terms of pure voice acting I think it's Date Everything. The game have a 100 different professional voice actors that want to seduce you.

Halo master fucking chief! Hell yeah brother

Crusader: No Remorse

Wicked good acting in general (it had full motion video sequences in live action) and just a criminally underrated game from the DOS era.

The entire Command & Conquer series when Westwood was still handling them, especially Red Alert 2.

GTA San Andreas has a few good ones my Favorite Being AXL Rose as the DJ from KDST.

But many suprising actors in there : Samuel Jackson, James Woods, Peter Fonda and Ice T:

https://www.behindthevoiceactors.com/video-games/Grand-Theft-Auto-San-Andreas/

Intro narration to Fallout 4.

War. War never changes.

Alan wake is damn good

I don't play as many games as some of you, but Christopher Judge as Kratos is my favorite.

For me, one 2001 game is lodged forever in my mind, Hostile Waters

It's a great game, although sadly won't run on modern systems. And not strictly voice acting, more narration, but I've just re-watched the intro and Tom Baker's narration still gives me shivers.

Almost a quarter of a century since I first played it, the phrase "These are hostile waters" in Tom's voice still pops into my head from time to time.

"Trust me."

I remember most of the super giant and double fine games having good voice acting. Jennifer Hale Femshepard from mass effect is a classic, and Matt Mercer does some great work with Edér and Aloth in pillars of eternity. Anything Keith David does is gold.

Resident Evil on the PlayStation

Isaac Clarke in the first Dead Space

Gabriel Angelos from the original Dawn of War

Not necessarily the biggest roles but I've always appreciated:

• The narrator in the original Medieval: Total War (intro for example). Set the mood.

• Prophet of Truth in Halo 2.

• Dunmer male voice actor for Morrowind.

The first and last especially set the atmosphere so well.

The female player character in Outriders was surprisingly very good. With the right face and hair, it was like Bobby Draper from The Expanse.

Too bad the rest of the game was kind of meh.

Not an actor, but the early voice synthesis was amazing the first times hearing it:

https://youtu.be/i1_fDwX1VVY

https://youtu.be/n3dq8I4uSw0

https://youtube.com/shorts/yA6OjZ8pTAE

Terry Bogard

Kreia from KOTOR 2 really gave an astonishingly good performance, as did Bao-dur in the game game.

I can't think of any game at the moment that was particularly notable across the board, but I can think of a few specific performances.

Kazuhiro Nakaya as Nishiki and later Ichiban in the Yakuza/Like a dragon series. He is fantastic at getting the character's personality across just in general scenes, and the emotional moments genuinely stick with me.

Rene Zagger as Emet Selch in FFXIV. That game has some fantastic performances but Emet Selch's is honestly one of my favorites. Every one of his lines is delivered perfectly. The arrogance theatrics that later tive way to genuine anger and sadness at what he's gone through. Along with more specifics I won't get into. 100%, A+ Performance.

Though, actually... Now that I think about it... The Persona 3 Reload dub is probably one of the best English dubs for a Japanese game in a looooong time. And generally they're pretty good these days. But that one nails it.

Disco Elysium has the best voice acting that's ever enhanced my experience. Others might be objectively better but never have I been so immersed in a story

Every actor in 'Still Wakes the Deep'. I don't usually like that type of game - you don't really have a great deal of agency, you can't fight only run, there are sudden deaths in some sections - but the overall atmosphere, the design, and that perfect voice casting drew me in. I think it's still on Game Pass if you want to see and hear it for yourselves.

All of the actors for Command & Conquer: Red Alert 2 were fantastic, but certain things stick with you forever.

Pretty much every voice actor in Star Wars: The Old Republic is really great

I played The Last Campfire recently. It's a small puzzle game and the only voice is the narrator, Rachel August. Maybe it's just her accent but I think her voice has a haunting otherworldly beauty that just makes the game.

Vampire the Masquerade: Bloodlines

Every Character in it has stellar voice over, I can't think of anyone who's just average.

Star Wars: The Old Republic

Has a great cast too. The voice behind Bastilar is also female Shepard. Her name is Jennifer Hale.

David Lodge as Grigori in dragon's dogma.

I don't even usually care about voice actors, but he did such a good job that I looked for him specifically in the credits and remember him to this day.

Path of Exile has some good ones, but the emperor that narrates the labyrinth and the captain of the ship that rescues you are my favorites.

I mean, the new Indiana jones is pretty incredible.

Death from Darksiders. But that's cheating.

Karen Dunbar - also a legendary Scottish comedian.

https://www.youtube.com/watch?v=OYQDnV092hI

The voice acting in Tangle Tower (a point and click murder mystery game) is 10/10

I have to plug in my favorite vg voice actor: Kellen Goff! A recurrent cast for the Five Nights at Freddy's franchise, and one of the best performances in League of legends! His range and vocal control is crazy, plus he looks like a really fun guy based on his multiple interviews.

Notable roles:
Fiddlesticks (League of Legends)
Arnold (Five Nights at Freddy's: Secret Of The Mimic)
Funtime Freddy (Five Nights at Freddy's: Sister Location)

And a really fun watch of him explaining how to do the Fiddelsticks voice: https://www.youtube.com/watch?v=czsRZd2-6Ac

I really love the Voice Acting in Telltale's The Walking Dead series. Just superb story and the actor's really sell a superb script. One of the better stories I've seen in Video Games.

A bit part, perhaps, but George Ledoux as DUNCAN FISHER MechWarrior 4 Mercenaries!