Ah, the age old "gotcha" that Windows users have always trotted out... Windows is better for games.
Could be true. There are certainly vastly more games that are Windows-native than there are games that are Mac-native. But there's also a heaping, steaming pile of dung that comprises the vast majority of games that exist (not just for Windows, mind you--the same is true for consoles such as Xbox, Wii, PS2, PS3, whatever).
The games that are worth playing are, eventually, ported to the Mac OS. Or a Cider version appears in the grey market, at worst. The downside, if you insist on playing a Mac version of a game, is that you have to wait until it is ported to the OS. More often than not, that means you won't get to play the game on the same day, month, even year, as your Windows brethren. The upside is that once it does make it to the Mac, all the bugs have been worked out, and you'll have a satisfactory experience from install through end credits.
But, thanks to the fact that all Macs made in the past several years, and all Macs made now and into the foreseeable future, can run Windows natively (you still have to install Windows, mind you), you can take your pick of games, and play them with aplomb and much gusto on a Mac. Even the ones that comprise that heaping, steaming pile of dung.
Bon appétit!