I'll bite.
I prefer using my 2006 iMac (under Bootcamp) for gaming over my powerful desktop PC. I invested a lot in getting it quiet, I build these for fun so I know what I'm doing. But since I play games at night after work I use the iMac instead. It breaks into a sweat but in 4 years it's never been too loud that I can't hear it over my games.
Also on my iMac I can run OS9, OSX and Windows games.
The iMac boots faster, smaller profile, uses less power, more reliable. Just the other week I tried booting up my desktop PC and it would crash on the Windows loading screen, it was missing a file and took about 30 minutes to fix which could have been spent having fun with my friends online.
My next machine will be a maxed out iMac for the above reasons. They're quiet, efficient and reliable (6 years in and I've never had a hardware problem with any of my macs or iPods).
I'm also more interested in how games work than how they look, I'm happy to play on the lowest settings to ensure a smooth and constant framerate (even on my best computer).