The wii is successful for the same reasons playstation was. A large part of the non-gaming population began to see videogaming as not embarrassing. First it was kids and teenagers of all kinds, now it's mums and grandmas.
Moms see Playstation as the cancer of children childhood, something that should dissapear. Give me one mum that hasn't said once "Are you still/again playing with the console???".
Wii is seen as a board game instead, as scrabble, as trivial pursuit... something that the whole family can enjoy and be proud of. At work I see everybody being "proud" of playing the Wii, while many people play PS3 or PC, but they doesn't tell everybody about it. That's what's making wii successful, its aim to be a family central console, and the fact that people is proud of playing wii, as with having an ipod or a nokia n95. It's just fashionable.
That's what's killing videogames, but hey, that's my opinion. Wii sucks, as many mediatic as fashionable articles. But I understand videogame ignorants to enjoy simple, stupid and repetitive mechanics. I enjoyed with shit like that in the eighties, why couldn't they enjoy them now?