Depends on what you mean. My favourite soundtracks to listen to are the Final Fantasy ones, specifically 8&9, but the best soundtracks are the ones you don't really notice, except in truly epic moments, but add to the atmosphere overall. Halo 3 really did this well, and the Metal gear Solid games also have really good soundtracks, but most of the tracks on both, are not ones you'd listen to for pleasure.
Assassin's Creed 2 also has a pretty good one, but brotherhood has a really irritating operatic voice in it that is utterly terrible.