Brian Oberkirch talks about What the Wii Can Teach Us About Making Great Web Apps. I think he's right, but with one caveat: the Wii is much better on a big screen.
We took ours on vacation over the holidays, and the difference between playing at home on a big HDTV and playing on a 20" TV is huge. You have to get closer to see, the gestures are far more sensitive when dealing with things on the screen, and the whole experience is lessened. My daughter kept whacking my son when trying to play tennis because they'd moved in closer to the screen so they could see in enough detail.
I think this is one of the most magical things I've seen in awhile, but I think its an artifact of large screens and worry that it doesn't scale down at all.