>>1
They've made WINE which was then ripped off by the Transgaming people. Problem is it's really hard to totally reimplement both the win32 API and DirectX, since you have to reimplement the bugs and undocumented behaviour as a lot of software depends on it. Case in point; Windows 95 had code specifically to make Sim City run properly, as the DOS version did some crazy shit that Windows normally wouldn't allow.
Of course the above assumes that when you say "games" you mean "Windows games." The way to get it to play games in the general sense is to run the native binaries. That's how I play NWN, Doom3 etc. It's not that Linux is somehow "bad" at games, it's just that most companies write for Windows and don't bother to port because they don't have the budget to cater for such a small market segment.