/vr/ - Retro Games

Another top choice might be Oddworld: Abe's Oddysee (and it's sequel, Abe's Exoddus). The game seeks to create an alien world and environment, and obviously sound is a major part. The music is mostly atmospheric and properly fits each zone. It has ambient noises in it like sounds that are clearly meant to be things like birds in the forest, although obviously not recognizable as real-world birds. The alien creatures make bizarre sounds that bring them to life. The protagonist's voice is iconic and helps build his character a lot, as a goofy character way in over his head.
I think the highlight here are the voiced lines, since they have gameplay value. It is one of the few games I can think of that has an in-game audio-based dialogue system ("GameSpeak") - you can issue commands or taunts to other creatures, who respond in kind, with each being given a dedicated hotkey. Your available "speech" changes depending on what form your character currently has, with there being around probably 30 unique vocal actions.