There are some that I like because they sound nice and others that I like because having them is useful for flash projects you may or may not be planning. Some of the ones I like because they're good are the BlazBlue soundtrack, the Soul Calibur 2 and 4 soundtracks, the Donkey Kong 64 soundtrack, the Professor Layton soundtracks (they're all pretty much the same anyway), and a good portion of the Phoenix Wright soundtrack.
Ones that I like for usefulness are the Brawl Soundtrack, the MvC 2 soundtrack, and the rest of the Phoenix Wright soundtrack.