How about this classic from Baldur's Gate 2: Throne of Bhaal? In fact, most of the music from both of those games and their expansions is excellent and adds a ton to the already fantastic gameplay.
EDIT: fuck me, I should totally be paying attention to repeat threads. This music still rocks though.
I use this and similar music when drawing something in PS For anything else... everything made by alexander Brandon and Michien van den Bos will do... (Unreal, Unreal Tournament 99, Deus EX, but those were already posted on page 1)
So I doubt many people know this song since I'm pretty sure this game didn't come out outside of Japan... Waltz for Aria, from Venus and Braves To this date the only game I bought b/c of the music.
Others:
Amazing music, solid plot, terribad story progression and overall system. SaGa Frontier II - Feldschlacht III
Dreamfall - The Longest Journey Besides being a totally awesome game (great story, probably the best voice acting I have seen in a game yet, I actually think that this game might the closest to "art" that games have come yet) it also has a killer soundtrack. If you haven't checked out game or music, definitively give it a shot.
The Game: Official Homepage Trailer : Here (too bad I have no idea how to embed youtube here - maybe someone can enlighten me?). It's kind of an...classical adventure game, with newer graphics (newer in this case meaning 2005 or something about that here, and probably wasn't state of the art to begin with, but its easy enough on the eyes). It's set in the not very distant future, the rest I will just let you find out on your own. There is also a prequel to the game, its far older, but you don't really have to know about that to enjoy this one.
thedeadhaji, you just reminded me how fucking awesome grandia II's music is and I am now listening to the soundtrack. Grandia II is probably my favorite RPG ever, just listening to this makes me want to hook up my dreamcast and start spamming purple lightning.
I can't pick a fav song from that game, but this is in the top 5