I think the Wand's problem is that it will end up another EyeToy, in the sense that it will build it's own userbase of games, sometimes rather good games, but not really break out and impact development on the console at large
Natal has a different problem, in that it seems to me that Microsoft is clearly drawing a line in the sand between Natal style games and the regular games that will continue coming. Fable III is the only thing we know of so far that seems to bridge the gap, but it seems like other 360 devs are just giving it lip service, like "yeah, you know, Natal is the future. But i want to get back to making my real games now." or something
Monster Hunter: pissing me off since 2010.