I Love my Mac and it does gaming just fine but not all games are ported to the Mac sadly. So you most certainly need a PC for serious gaming. I have a Mac and a PC at my desk because of this. Best of both worlds.
That said... The Mac is going with Intel processors in 2006 and it "will" be able to dual boot into windows without the emulation issues of the past. So in the near future the Mac will be just as good at gaming as any PC on the market. When you done flying Lock-On you'll be able to boot back into OSX and enjoy.
;)