I like game soundtracks that not only stand well on their own, but truly immerse you in the game:
- Planescape:Torment... one of the most evocative and inspiring soundtracks out there, an inseparable part of the whole experience
- Command & Conquer 1 (incl. Covert Ops)... arguably the most eclectic and fun combat music ever -- classical, jazz, hip-hop, industrial, even some grunge
- American McGee's Alice... perfectly sets the mood and atmosphere of a twisted fantasy horror story
- Unreal 1... great mix of traditional and futuristic elements -- I developed quite a bit of respect for the talents of the MOD/tracker community after hearing it