Unless you're going after nostalgia, already released games, a handful of ports, or are really into mini-games and gimmicks, there's no reason at all to buy a wii. It's an overpriced paper weight now
Xbox live also seems to have a fuck of a lot more people on it than the Playstation network. So if you're into online games, go with the 360.
I like that the ps3 has a blu-ray player, but I don't even want one of those right now. Movies won't be blu-ray only for quite a while.