PS3 - It's been out for a year and has a small catalogue of games which I don't see changing anytime soon. And all of the good games you can get on the 360. Unless your into the Blu-Ray bullshit, I'd steer clear.
360 - Probably the best choice. But if you don't like Adventure/Racing/Shoot em up games then it's pretty lame because that's all you can buy on a 360. But Gears of War probably makes up for things. And the online is top notch, despite the annoying kids and adults who act like kids.
Wii - My personal choice because I'm a fan of varity and that's what I get with the Wii. Great games, good price, great innovation. Plus, there's a BUTT load of awesome games coming out for it.