Now, before I say anything let me say that I have been pure console all of my life --I am now downloading "sauerbraten" to play around with now, and previously have never endeavored to seriously game on a computer (I messed with Second Life, Runescape and a couple of other free MMORPGs too...).
But anyways, besides game-specific distros like
live.linux-gamers.net and
cedega (Cedega's not free...), Sabayon does quite well. I think my internet is slow (so much better than the dial up from my past), but even the early build of Second Life seemed quite functional.