Your on your own...the genres are freaking everywhere, and theres no tagging system here at OCR, though that would be convenient. As far as games go, you'd probably be best off just putting "Kirby" or whatever in the search filter, since the naming system for ReMixes puts the name of the game first in the song title.
If you want some extra advice, I say screw organizing mp3s altogether. That shit sucks.