Get an Xbox360, the Wii is just a gimmick, beleive me. It'l be fun to wave a remote control around for about 2 weeks, after that either your arm will hurt or you'll get over it. The controls aren't that innovative either, I,ll take Wii sports and Zelda for example. In wii sports, you just swing your wiimote in whatever direction you want and it'll swing the tennis racket, just like pressing a button. Same in Zelda, whenever you swing your wiimote, it's just like if you hit the A button, it does the exact same thing, Link doesn't swing the same way you swing the wiimote. Not only that, but there aren't any really good games out, and there won't be a lot, just like Gamecube, in my opinion.
The Xbox360 on the other hand is a much more solid console, it's got lots of power to run graphics and physics intense games, unlike the Wii, and has a lot of excellent games coming its way, like Blue Dragon, Lost Odyssey, Bioshock, Mass Effect, Eternal Sonata, Virtua Fighter 5, Halo 3, Devil May Cry 4, Army Of Two, Call Of Duty 4, Star Wars : The Force Unleashed, Burnout Paradise, Assassin's Creed, Rock Band, Guitar Hero 3 etc. It already has a lot of good games for it, like Gears Of War, Lost Planet, Rainbow Six Vegas, Forza 2, Dirt, Overloard, C&C 3, The Darkness, Ghost Recon Advanced Warfighter 2, etc.
IMO, you're getting the best out of your money with the Xbox 360, not only because of the games and graphics/physics, but also because of Xbox Live, you can either pay for Gold, which is 24/7 access to online servers, voice chat for pretty much every game out on the 360, or you can play on Xbox Live Silver on week-ends for free. You don't pay for nothing though, you get servers and maintenance for every games, downloadable content such as maps, quests, cars, add-ons and expansions and patches. It's well worth the money.
I know I may sound like a fanboy, but all I said is true and is one of the advantages of getting a 360.