Well. I haven't picked up the Xbox360 yet, so I'll avoid it for now.
As for the rest of the current systems out there. Xbox is my favorite. Better graphics than that of PS2. A large variety of games, although maybe not as many, nor does it have some of the Japanese games that you'll see on the PS2. Probably the best thing about the Xbox is its controller. It has the best joystick, and the controller isn't that akward, and doesn't need much getting-used-to.
One thing though, about Gamecube. It's a must-have for me, because it will have games neither the PS2 or the Xbox will have. Most people don't give it credit for that, mostly because they don't like those games that are Gamecube-only. Kudos to GC either way.