Prince of Persia, Sands of Time trilogy. Yes, even the second and third games. Granted, the Warrior Within had a lot of that 'rock music' that critics loved to hate on, but if you really listened to the background music when the rock music wasn't playing, it was absolutely gorgeous and really helped set the tone for the gameplay. (too bad that technical bugs really worked against the appreciation of the soundtracks in those games)
And I must admit, practically anything by Nobuo Nematsu I enjoy (too many games to list!) Yeah, my phone plays him too.
Still, though, gotta love Zelda. I loved playing to the games to here the themes.
EDIT: Oh, yeah - one of my favorite game soundtracks is from Hotel Dusk, a little known, practically forgotten Nintendo DS game. The music is great though, and went further towards enhancing the gameplay than (sometimes) the game itself.