The Witcher 2 has a really good soundtrack. I love the regicide theme and "a nearly peaceful place".
Also, the mass effectseries has an outstanding soundtrack. From the music that plays when you're made a spectre in ME1, to the suicide mission in ME2, to "leaving earth" and "an end once and for all" (extended epsecially) from ME3, I'd say the ME series gets the crown for best game soundtrack.