Wii has the best games library for my taste (360 is close), and has the freshness no other console currently has for me.
I also own a PS3, but I kind of dislike it. GTA 4 will make sure my PS3 will get my full attention for the coming weeks though, no time for the Wii anymore.
I'm also a PC gamer, having pretty much a game beast hardware-wise. Though, I mostly play older games, like Baldur's Gate and Heroes of Might and Magic 3.
I would like to own a 360, but I think's it's overkill, and I'm afraid of the RRoD.