Something about game consoles brings out the inner fanboy in nearly all of us.
It all comes down to game preferences...
The Wii is totally different obviously. It's fun, but there aren't enough games that justify it as a primary choice imo. It's a great party console though.
The 360 is my personal choice because I tend to favor shooters/racing more than other genres. I also like the controller and the online networking more than the PS3's.
If you like japanese-style action/adventure/rpg games then the PS3's for you. Added bonuses are Blu-Ray capabilities and the fact that if you've every touched a PS in the past ten years you'll be familiar with the controller.
Graphics are split by a hair at the moment. First-party PS3 software has the potential to look better than what the 360 can do, but it's yet to be pulled off. Killzone 2 might do this though. Still, the PS3's graphical capability is hard to tap, and it'll be maybe another year before we start seeing any gap form between the PS3 and the 360.