In this interview, I was surprised to see Carmack highlight one of the reasons why 3rd parties have a hard time competing on the Wii/DS; the fact that Nintendo makes top-quality games for Wii/DS.
While this was discussed a lot in the forum a few months ago it was starting to fall out of fashion as an argument, so it was interesting to see that some developers do worry about this.
My Mario Kart Wii friend code: 2707-1866-0957