Depende ra na sa imong games and gameplay na ganahan. It's really up to you. If you're on the more interactive gaming, cutesy stuff, funny, cartoony, not so serious, etc. go for Wii. For serious awesome kick-ass games go for PS3. Although both got all those but it a matter of your own preference. The two systems are really different from each other so it's easy to decide which to get once you know what you really prefer in gaming. Otherwise, if you don't want a console why not kick ass on a high end PC. LOL. j/k
xbox 360 on the other hand, got so many awesome game titles. But be wary of the 3RL/RROD, choose your unit wise preferably the one with the Falcon chipset or else get it modified to have a nice cooling to avoid 3RL/RROD.
For me personally, I'd go for Wii but that's just me and my opinion. Mario (FTW), Samus (sexy), Link, Zelda, Donkey Kong, and most of all if ever Monster Hunter Tri would be imported in english... that would be freakin' awesome as I'm a monster hunter fan. I've only started on the PSP though. haha