Blizzard tends to be good at porting over their games to the Mac, the same goes for EA(apparently they have some sort of contract with Apple now), but other than the occasional Microsoft classic(i.e Halo CE, Fable), very rarely do most game developers bother to port over to the Mac, and even when they do, it's a terrible delay.
So, IMO, there isn't now.
But Mac and PC use to be close competitors in the gaming industry(yes, I know they're the same thing...).
EMZ=]