I guess it depends upon what you're looking for. Games like Gears and Halo III sell in large amounts on the 360 while games like Madworld and No More Heroes that would pass 1 million on 360 don't do so well on Wii.
On the other hand games like Brazt Party Babies, Wii Fit, and jrpgs sell much better on the Wii than they would on the 360.
Heavens to Murgatoids.