There are so many goods points made by Wired’s Chris Kohler in regards to Nintendo in this article that I’m not going to do the usual 100% regurgitation. Instead, just read it, paying close attention the remarks made by analysts from EEDAR and Kohler himself.
Synopsis: Sequels just don’t work on Wii; some third party developers aren’t trying because they believe “casual gamers” is a real term and therefore means a half-ass effort; some third parties did incredibly well if you look beyond the top 10; and, no, sorry haters, there’s no slump or bottoming out happening with any Nintendo consoles in the near future.
Basically, if you want to create a great game on the Wii, you need to create a great, original game on the first try. Then, resist the deep rooted desire to create yearly sequels, because the Wii audience is too smart for that. Enjoy!