Without physical feedback, the only really useful area for motion control is in RTS games. And I don't see them topping any lists outside the PC. I played a Wii at my friend's house awhile back and after dusting it off (He hadn't played it for like 6 months, whereas his 360 gets daily use) we played it for a couple of hours. Yeah, it was okay fun. But it's not doing anything for gaming, it's just being a reasonably enjoyable aside for a couple hours. I wouldn't buy one and as far as I know, my friend hasn't touched his Wii in the six or so months since we played it.
I have no interest in the Wii, no interest in Natal, and no interest in Move. I maintain my position that this whole thing is like if the entire industry had jumped on button mashing 15 years ago and companies based their business model around selling International Track and Field.
Which I'd rather play than play a Wii.
Edit: But even thinking about RTS, the whole point of our control systems is to be efficient. If you have a counter for how many buttons you press and click over the course of a game, it's going to be huge. If I'm playing something for hours it doesn't really matter how good the motion controls are if they make my hands sore.