@ sooper, the best online gaming is to be found on the PC, it really is as simple as that.
Wii's are great fun (for a while) and it's the only console you'll ever see your granny play. Plus they're backwards compatible with the Gamecube so there's a ton of awesome games available.
The 360 is vastly more powerful, has a ton of great games but it's (the pad rather) best at shooting games (Call of Duty, Halo etc) it's also a bit on the noisy side, you have that huge brick of an external power supply and you have to pay for the online service, which in this day and age is not cool (it's a way of getting extra money out of spotty teenagers because their parents pay the internet bill)
The PS3 is the most powerful of all and it does more than the rest. Multiplatform games are virtually identical to the ones you'll find on the 360 but the exclusive titles are just mindblowing! The PS3 (pad) is not as well adapted for shooters but it's better than the 360 at everything else. It's almost silent, it has bluetooth (something which until you use it, you don't care about) the online service is free, it plays Blu Ray discs (amazing!) and it supports BBC iPlayer, LoveFilm and it has a built in web-browser (the 360 doesn't)
Playstation 3, it only does everything.