Before anyone claims it's only the core, the enthusiasts who suffer from a lack of support, that's not exactly true. The major droughts for the Wii happened in late 08, and through 2009 (mostly early 09). I have charts of Wii YoY comparisons throughout those two years, and the visible declines in Wii momentum correspond with those droughts (with a little lag), they appear as large troughs in the graph.
The Wii userbase in general suffers from this. Nintendo failed in late 08 with their two big games, and there wasn't any big third party games to pick up the slack as could be expected on the over two year old market leader in 2009.
A game I'm developing with some friends:
www.xnagg.com/zombieasteroids/publish.htm
It is largely a technical exercise but feedback is appreciated.