As one of the token Mac users here, even I would agree that if you are hardcore gamer, the PC is the way to go. There are some good games that run natively on Macs (Civ IV being my favourite) but not many compared to the Windows environment. Most Macs are not as upgradeable as generic PCs (the Mac Pro certainly is, however).

Parallels, which is the virtualisation software you may have read about, does not really do 3D games well at present. Boot Camp requires you to have a separate partition, and both need a full copy of Windows to run Win games (which is pretty expensive on top). Sadly, Apple's implementation of X11 is rubbish, so despite Mac OSX being Unix based, WINE doesn't run at all well, so you can't use Linux as a free guest OS under Parallels to run games.

Garageband however, is a very sophisticated piece of kit and well worth having if you are into music production. But then Macs have always excelled for creatives.

I love Mac OSX and hate having to work with Windows, but I do miss the range of games. However, the ancient games I like to play often have a Mac port (BG series for example) or will run under Parallels (MTW). I've had M2TW run nicely on my Macbook Pro under Boot Camp, but I chucked that because it was so poor, challenge-wise. So, no loss for me, as I haven't seen a decent strategy game produced for years aside from CIV, and that's on my Mac!

As ever, it's the tool that works best for you, and if you game, there's no contest, as the others have said. Anyway, as a hardcore gamer you won't be going out much, so you won't need the cool looks of a Mac