I prefer the Wii over PS3/Xbox 360.
Why? Well it got fun games like Twilight Princess, Mario Galaxy 1 & 2, Super Smash Bros. Brawl, New Super Mario Bros Wii, No More Heroes, Wii Sports, Monster Hunter Tri, and lots more.
There's some Wii games coming out that gets me exited like Skyward Sword, Kirby Epic Yarn, Donkey Kong Country Returns, and Epic Mickey. Hope these games don't disappoint me.
I can also play classic games that's originally released on NES, SNES, and N64 as well on the Wii.
PS3 is alright, but there's not many exclusive games that I enjoy and only ones I enjoy are Valkyria Chronicles, Demon's Soul, and LittleBigPlanet at the moment. I just have to wait until there's other exclusives coming out that's looks interesting.
I don't hate the PS3 at all, but I don't like it as much as PS2.
I use to own an Xbox 360, but I sold it to my older brother since I can't find any good exclusive games and there's haven't been one upcoming Xbox 360 games that interests me.
In the order of 7th gen console from my favorite to my least favorite.
1) Wii
2) PS3
3) Xbox 360
That's my opinion.