Well for the Wii I'd go like this:
2007>2009>2008>2006
I mean 2007 was really epic, it had Galaxy and Prime along with things like Super Paper Mario, Excite Truck, RE 4 and many others. 2006 had the launch titles which were great, but not enough to top the other years. 2009 had WSR and NSMBW above many others, 2008 had Kart and SSBB so these two years are close I guess.
Of course 2010 looks like it will become the best year with Mario, Zelda and Metroid along with many great games from third parties.