Big Brain Academy: Wii Degree is at 2.33 million right now, haven't seen sales lately but don't think it will reach 3million (unless Nintendo releases a player's choice edition that cost 20$)
Nintendogs could have the same sales and still the profit coming from it would be huge, so of course it is worth developing. Even if it sells only just 1 million there will be a big profit, but it's guaranteed to sell more than that!








