Mption controls suck because developers either try to force them into types of games that have evolved and play well already without them; or focus entirely on the motion controls themselves and forget to actually design a decent game to go along with them. And even when motion controls work (ie; wii sports) it's in a casually fun way that doesn't really make you think, or engage you in any kind of experience. wii sports and boom blox are great, but they're not gonna affect people as deeply as MW2/ME2/MGS4/P4 (or whatever other story-based game you like).
 
One of my favourite games on the Wii was Endless Ocean, even though I know it sucked, it was small, and the graphics were bad, and there wasn't a great structure to it, the wii controls went great with the placid experience of poking around in the sea. Milo actually works as a demo for Natal too, because it shows proper interaction with a game environment in a non-competitive way.  

My point is, I think Natal would work superbly if they ditched the idea of making a 'game' according to conventions with Natal, and simply created some other type of experience. Perhaps a world in which you can simply explore and engage with characters, kind of like the boring bits in Shenmue, or something like reading a slow-paced detective novel, with you doing the interrogations and investigation of scenes - I dunno, I ain't thought that far ahead. Basically just don't make me motion shooting a gun or punching people in my living room, cause I'm not that bored.