None of the above
PC all the way, everyday!
A good PC can play more games than any console, most of the games are open source (legal modding ftw!), there are usually more mature communities, games tend to have more content, online games tend to be more accessible etc.
If I had to chose though, I would go with Xbox. PS3 has better graphics and stuff, but Xbox has a better library of games. Some of my favorite games are on Xbox. Wii has some fun games, but I feel like Wii is that friend that you have that never grew up.
In the end, my laptop will bring me much more enjoyment than any console, I mean, I can use the internet from a PC (I can use the internet effectively from a PC. I realize that the consoles usually have some sort of internet application, but they are worse for actually using the internet than my cell phone).