Mass Effect's soundtrack blew me away; the Metroid Prime series's is also pretty good, but I still always go back to Super Castlevania 4 on the SNES when I have to give an example of good music in a game.
Note: I also would like to mention Castlevania: SOTN, that was impressive too.
Note: I also would like to mention Castlevania: SOTN, that was impressive too.