Rills
Sentinel
Morrowind Soundtrack 2 catches the essence of exploring Morrowind in all its "othernesss." Just listening to #2 brought back memories of transversing the landscape with a sense of trepidation.
Stones from the Ultima Series is one of my favorites as well, even though I have never (!) played one of those games (I know, shame on me).
Realms of Arkania
Catchy soundtrack, the hum-along kind.
Examples: A New Life Is Born (RoA1), Diary (RoA2) and Pondering in Solitude (RoA3)
Divine Divinity
Incredibly diverse and slightly melancholic music.
Example: Sighs Of The Elvenkind
Diablo
Oozing with atmosphere.
Example: Tristram Theme
Actually, the Tristram Theme may be my most favorite of them all.
Arcanum gets an honorable mention because its soundtrack was certainly unique.
Interesting to see so many people list Gothic 3 as their favorite. While I agree that G3 had excellent music, I preferred the sound of Gothics 1&2.
I haven't seen Mass Effect mentioned. Both games had good music, but the Kraftwerk-like tracks of the first game struck me as quite unique considering other games I played. Mass Effect 2's music has more of a Blade Runner feel to it, also nice.
Morrowind/Oblivion had some very good music, as did Final Fantasy 7.
Am I the only old coot that remembers Alternate Reality?
Oh yes … I wanted to do a music video with that song plus maybe Valley of a Thousand Rivers, also from KB, with footage from The Last Unicorn. Perfect synergy. Haven't gotten around to it yet though.Well, it's not really an RPG, but it has been reviewed here ;-) Some of the themes for King's Bounty:The Legend - well, one in particular: Under the shadow of an Oak
(http://www.youtube.com/watch?v=_jyDFm_FTws) - it was the combination of music withe the tranquil elven forest…I found myself going back to that area just to listen to it! (and look at the pretty sparkly unicorns…oooo pretty!)