the use of the word "better" is always problematic because you then have to explain how you define "better," which you did; then you have to justify it, which you did; but it has become entirely subjective during this journey. the hurdle is truly justifying why "tactical gameplay" or "character interaction" has more value than original world building, which is nigh impossible.
considering this is computer games, you could make the argument that gameplay rules all, but doing shooty-shoots-at-bad-guy can happen regardless of setting, it's all about mechanical fidelity and input-response feedback at that point; the setting is not relevant. if someone plays a computer game primarily for its unique setting, then the uniqueness of the setting becomes the prominent value judgement for that individual; that person would be disappointed if the setting was just a DnD-rip, for example.
i do think there is merit in your viewpoint from a general perspective; to appeal to the masses, using familiar tropes helps ease the average player into a comfort zone. but too much reliance on this idea of "familiar is better" stifles creativity. you could argue that unique settings should be left for novels/etc, but i think computer games should push boundaries, and the idea of what constitutes a computer game changes every day. you could argue that a non-DnD setting falls into the realm of "scifi" as well, but this is a semantics game; genre labels are typically vacuous, functioning only to give a potential audience some general understanding of the material they're about to engage with.
that being said, i can't think of many "fantasy" settings that don't borrow from Tolkien on some level. even the example i was going to use to counter your point, Morrowind, has a setting heavily inspired by Tolkien; albeit, very far removed and unique with elements of Hinduism thrown in. i don't think this validates the theory that sword/sorcery settings are "better," only that it validates the theory that human beings have a hard time being truly unique. even Tolkien was heavily inspired by the Norse Volsunga Saga. it's like a long game of telephone.
good post.