I don't think switching is what you really want to do. Sad to say that gaming is just not something that Linux is real strong on. And there's a lot of reasons for that, like distribution contracts and copyrights and the general attitude of many Linux users toward games in general. For at least the time being, games are going to be played on Windows machines. And if you want to game (but don't want to write your own game), you're pretty much stuck with Windows. Some people will tell you about Wine or Qemux, or Crossover, and those do work, but in the end, a gamer without Windows is like a car without headlights - you'll always be lost and behind. Sorry to break the bad news to ya.
**************
Now, personally, I think gaming is stupid, and that you should wait until you want to do something interesting before you start talking about switching. Wanting to be a Linux gamer is like going to McDonald's and ordering burgers with no meat - you've given up the item, but not the concept. Of course it isn't my place to tell you what you should and should not do with your computer. This is just down here in case you want my opinion instead of my advice.
{[(edited - thanks PiratePenguin)]}