Motion controls vs. Console controls is a different version of arguing Console Controls vs. PC Controls. You sacrifice variety and some control for ease of interface. The ease of interface in motion controllers is phenomenal for simple games that can attract people that don't want to memorize control schemes on a game-pad or keyboard. The problem is that most "hardcore" games need the more complicated interface to provide a depth of mastery to the game.
I'll use Dragon Age as an example. Can you imagine playing a title like that with a motion controller like the Kinect? I'm no developer, but it seems like an impossible task to work in the controlled character's powers along with the abilities for party tactics and switching. Also, going back to my intro sentence, playing on the PC has more depth, but more to memorize by way of what keys do what actions. Hybrid systems could fix this, but may also create a different problem where constantly switching between control schemes becomes a bother.
I think it's possible for "hardcore" games to be made for the Kinect, but I don't think developers will be able to think outside the box enough to make them good. At least not for a few years, yet.