Once one fat lady shows up at her work and she's lost a ton of weight and all the other fat ladies say, "wow you look great, how did you do it?", and she says, "I bought wii fit", all the other fat ladies will buy it and it will be like a nuclear reaction of wii fit buying. The fat lady market is huge. Look at the diet industry and the fitness equipment industry, If nintendo gets 1% of those markets, wii fit will outsell the PS3.

Wii Fit isn't just amazing for being the game it is, there is also another touch that will give it, and other games, great legs.

Guy W: OMG! Game X is comming out for Wii, and it uses the balance board, I have to get that game! Wii Fit sounds kinda meh, but I guess I'll buy it as I really want this game.

2 months later:

Guy W: It is kind of a waste really, to have payed 30-40 dollars for a Wii board when I'm not really using it for more than game X, I guess I'll buy another game for it.

This guy now bought 3 games instead of 1, because of the Wii balance board.

Then there's guy C

Guy C: Wii fit is awesome, I'm so glad I bought it 3 months ago, it's the only game I've played since that. The board is one of the best additions ever! I'll go to my close store and check if they have some games using the board.

This guy now bought an extra game because of the balance board.

So as you can see, the board is a geniousity far beyond just Wii Fit.

While I think Wii Fit will do very well, I'm a little hesitant to make predictions like it outselling GTA4 this year, or the PS3 lifetime. I'd like to see whether they actually get that rumored Oprah endorsement, first. ;)

I think that eventually Nintendo will have to find a way to offer a Wii/Wii Fit package to *truly* get to the Mom/causal exercise crowd.