As a trained (if not particularly good) musician, I can definitely say that Wii Music is closer to the real creation of music than any other game I'ver ever seen. I'm not sure if that makes for a more FUN game, but this really is an amazingly innovative product.
You'll learn more about chord analysis in five minutes of the video that puffy posted than a lifetime of "repeat this rhythm" games like Guitar Hero and Dance Dance Revolution. (And I say that as someone who absolutely loves DDR.)
End of 2008 totals: Wii 42m, 360 24m, PS3 18.5m (made Jan. 4, 2008)