I wouldn't go so far as to call motion sensors a gimmick. They're in desperate need of refinement, but I think there's a good future for them (if only for games that are compatible with such options).
I was sort of upset when I played Zelda for the first time on the Wii, thinking I'd be able to have some sort of control on how my sword was swung. Like many people, I'm sure, I just sort of fell into the routine of jiggling my wrist a little to get him to swing. It wasn't any different than pressing a button on a controller. The Wii Sports had some good ideas, but the hardware needs improvements before something like a legitimate boxing game can really hit home.
(Boxing, by the way, would ROCK on motion controllers!)