I finished Quake 1 with all its official add-on content and while it was interesting to play, I liked the older original Doom more.
The big difference to Doom is of course the real 3D levels with 3D enemies, which changes how you can hide from enemy fire and how the developers can place enemies and traps. But sadly, colours, as in plural, were too expensive back then, so the only colour they could afford was brown. Meaning everything looks so boooring, as there are few highlighting colours to contrast against. Brown castles, brown caves, brown labyrinths, brown outer dimensional planes.
The enemies are eyeless lovecraftian monsters and have different attack types leading to the player having to switch how to approach each fight depending on enemy composition and level terrain. But I did not enjoy the slower pace and more methodical approach in contrast to Doom's more hectic Run & Gun gameplay. This is strengthened due to the smaller rooms and more tunnels and hallways.
I was surprised that the levels were, similar to Doom, more atmosphere than logical and coherent layouts, but the level packs luckily improved massively there. Inside those, there was a red thread flowing through the levels and a certain rampup of difficulty and setup in the level progression. This is in opposition to the almost random feeling composition and combination of levels in the base game's chapters. And the newest level packs from the last decade really show what is possible inside the engine and how much level design improved from the birth era of the shooter genre.
I also enjoyed the secrets inside the levels and how they were often possible to be found by paying attention to the environment and noticing odd parts.
Would I recommend playing it nowadays? Not really. This game was the first steps into a new genre and they didn't yet found what works and what doesn't. If you are interested in the birth of the shooter genre, sure, but it's not a hidden gem that was unfairly forgotten in my eyes. The quake engine with its tons of fan made levelpacks though? That is another thing entirely.
