Wii>PS3>>>>>360
Wii has the greatest exclusives of the gen, by far. Super Mario Galaxys, 2 Zeldas, NSMBWii, Monster Hunter Tri, Xenoblade, Goldeneye (no longer exclusive), Donkey Kong, Kirby, Brawl etc...it may not have to multiplat, but it more than makes up for it in exclusives. There's games for everyone, and for the price, the GC support and for the VC, I have to give it first.
PS3 not only has good exclusives (Ratchet And Clank, Uncharted, Gran Turismo), but also some good mulitplat games, which I shan't list. However, the exclusives aren't quite as intuitive as those on the Wii IMO, and the inability to play PS1/2 games means it just misses out on first.
I had a 360, but sold it recently. The exclusives library was pretty much non-existant, the controller felt clunky and with only 256MB of onboard memory, in addition to having to pay, we never really went online. So the 360, whilst a good console in its own right, is the weakest this gen for me.







