I find lots of video game music deficient of quality. A lot of it's just to do with what you listen out for in music, probably. For example, my brother, an avid fan of film and game music, tends to get "stimulated" (for lack of a better word) by music with loud bass, big drums and blaring brass without there being an emphasis on melody or anything. A lot of what he plays would really bore the hell out of me. On the other hand I can get excited by the amazing counterpoint of the Brandenburg Concertos but my brother wouldn't at all appreciate it. Our tastes aren't so mutually exclusive, however; we overlap at Stravinsky or Shostakovich.
Having said that I'm sure some game music is good but I just haven't really been exposed to it yet.