The only thing that is wrong with the Playstation 3 is its price. The Wii is priced such that I could pick it up on anytime if I felt like it, without worrying much about the money. The Playstation has a price tag that makes me think twice before I will purchase it.
I don't even consider the XBOX 360, despite the great XBOX Live Service. Its games, all in all, do not appeal to me. In my opinion, it does have neither the great Nintendo titles, nor the awesome performance of the Playstation 3.
In my opinion, PS3 beats the XBOX 360, hands down. PS3 has an online service I don't have to pay for, and its performance is superior.
The Wii and the PS3 are hard to compare, if any at all. At half the price, the Wii is an entirely different product. Also, the Wii is a video game console, while the PS3 is a home entertainment system with BluRay support. I think that both systems serve different markets, that overlap only partially.
In my opinion, the Wii will surpass anything and everything in the long run. I was enthusiastic about the system even when everybody on Slashdot made fun of its title, which I still think is great. XBOX 360 and PS3 will fight for 2nd place, which PS3 will eventually win, unless the XBOX division gets a major cash injection by Microsoft. Face it, not everyone likes WWII shooters/sims/rts titles.
As a vision, the PS3 is unique. It shows what home entertainment will be like in a couple of years. Unfortunately, the technology of tomorrow is yet too costly, today.