The problem is that the market is fickle. If you get a AAA game that only sells 1 million on an HD console and then comes out with another AAA sequel you can be pretty sure that the sequel will sell well too. This is because the games create a fanbase that consists of a demographic that keep up to date on the gaming world and know to support the developers of their favorite games.
This isn't true for the Wii. The biggest 3rd party sellers are mostly carnival games and you can be pretty sure that the moms that buy those games don't care which company or developer they buy from. Even the critically acclaimed games though aren't for whatever reason building this fan base on the wii. Games that start off low but keep selling due to word of mouth are there but then their sequels come out and instead of starting out with a bang due to an established fan base you get that same extremely slow sales trend. Just look at NMH2's release this week as an example of that. Getting to a million on discounted and bargain bin sales doesn't cut it for these developers.
The definitive evidence that video games turn people into mass murderers