I own a Wii and I never play it, XBox 360 and PC (even PS3 if I owned one) are just much more appealing to my gaming tastes.
It is "fun" for casual gamers and a younger audience. Dont expect Nintendo to have the same success with a similar console in the future. Many "casual gamers" I know who bought a Wii lose interest with it over time, so they wont rush out and pick up a Wii 2 for themselves next generation. The younger audience will always be there, though, as will Nintendo fans.
I like to compare the original Nintendo with Wii, it was a huge fad sucess when the gaming industry was floundering, but Super Nintendo, N64, and Gamecube showed a continued decline in sales as past Nintendo customers either went elsewhere (Playstation, XBox, PC) or simply didnt participate in later generations.
