I agree that SMG's motion controls (well, the Luna Spin) felt tacked on, but there's plenty of other examples in that game that work really well.
Aside from the Luna Spin the only other motion control I can think of in SMG is that unplayable broken piece-of-**** manta ray level. Surely you're not suggesting that THAT worked really well.
Motion control is like this idea that sounds really great in theory and that it would inspire all sorts of cool ideas. But then when it comes time to make a game that uses it it's like "uhhhhhh..." Wii Sports has to be scaled down because you can't really swing the remote and have some way to move the character. You think of epic sword battles but then realize to provide the proper accuracy the player would need to know how to fence in real life. Ah, but you could simplify it but then it's basically mapping gestures which is really no different from a button press, except less precise. Waggle is Nintendo thinking that Mario will benefit greatly from motion control, sitting down to make the game and then realizing that it really inspires no new ideas. So they tack on a "shake" that would normally be a button press and hope no one notices because aside from this controller they really added nothing new to their new console.
I think the biggest issue is movement. You can swing a sword or a baseball bat but how do you move? It's not like you walk around on a treadmill. Kinect has it even worse because you can't add any other control elements. The whole concept is limited like a lightgun. In theory a lightgun seems perfect - you shoot at the screen. How intuitive! Except how do I move my character around? Uh, I can't and that's why lightgun games are just glorified shooting galleries and FPS games that use more conventional controls have fulfilled the concept better than lightgun games ever have. These concepts are too limited and that's why we got so much waggle and shovelware crap on the Wii.