My Dad's first computer (I'm 19) was a Mac, so I was brought up on them. A coupla years back, I build myself an AMD box to get into the world of pc enthusiasts, gaming, overclocking, and the like. Now I'm in college and I've got a Powerbook, but will probably build another pc within a year or two. I will never be without a Mac- I'm now extremely familiar with both platforms, so believe me when I say that Windows really, really does suck. Things are just more intuitive on the Mac- files are laid out logically, everything is plug-and-play, and it's just attractive to look at all day (which I do). This isn't to say that Windows isn't functional- especially with 2000 and XP, if you're not an idiot, you won't get a virus or have to constantly deal with popups or spyware. Of course, if you are a computer-idiot, you're way better off with a Mac, because you don't have to do anything to avoid those.
As far as gaming goes: hardware is much more expensive, there is only one supplier for it, video card selection is miniscule, you have to have a PowerMac (read: expensive) tower to upgrade anything internally but your HDD and RAM, and while we now get almost every AAA title, there is a wait time for the port, and they never seem to come down in price. And forget any kind of useful overclocking.
Of course, most of that is irrelevant with the new Intel-based Macs and BootCamp. Anyway, it really comes down to budget. If you're a hardcore gamer, aren't willing to have two computers, and have a limited budget, then you should probably think about whether or not a Mac is for you.
If you're thinking about laptops, however, you're an idiot if you buy anything that's not a Mac.