Good games sell is a little bit too simple. A game needs three things to succeed on any platform. It needs to be well made, marketable, and fun. If a game only has two of those qualities it will have a tough time selling, and with only one it will most likely fail.
Many of these poor selling Wii games are both well made and fun, but not marketable. It's hard for us to tell what's marketable because we're the enthusiasts, we know about all the games. Marketability also should include how much it is marketed too, now that I think about it.
A game that appeals to the average consumer, is well made (easy to play and bugfree), and is fun to play (to the average consumer again) has no reason to fail. If your game doesn't match those criteria you did something wrong. What succesful games don't match that criteria?
"Now, a fun game should always be easy to understand - you should be able to take one look at it and know what you have to do straight away. It should be so well constructed that you can tell at a glance what your goal is and, even if you don’t succeed, you’ll blame yourself rather than the game. Moreover, the people standing around watching the game have also got to be able to enjoy it." - Shiggy
