Technically (unless you count the awful gamecube controller), the age of gimmicks started with the Nintendo DS. It hit infancy with the Wii, and now it's approaching adolescence. We're still firmly stuck in the age of gimmicks really.
I really don't see how people can not see the potential of Natal. How about Dance Dance Revolution without a floor mat, or even a fantasy fps where you cast spells with gestures and swing a plastic sword that actually appears to cleave through your enemies? That's ignoring the sheer awesomness of controlling your movie and music playback with gestures or voice. Sure, I don't buy that there's that much potential for full blown games without any form of controller, but combined with a simple thumbstick and trigger (like the wii nunchuck, as much as it pains me to say it), we're talking the ability to combine something like house of the dead with a full blown FPS with full interaction. Want to shove a zombie to the right and then punch the one behind it? Go for it. Wanna throw a grenade at its feet and then duck as its body flies over you? Sure, go right ahead. With a little imagination there's a heck of a lot of potential there.
How about interactive martial arts training? Sure it wouldn't technically be a game (and it wouldn't be able to replace proper instruction), but it'd certainly be better than any similiar software on the wii. It could make sure you were performing every move correctly, and you could even 'spar' with an on screen opponent.