First off, being that a well designed motion controller should be able to encapsulate the functionality of both the Wiimote+Nunchuck as well as the functionality of the XBox 360 and PS3 controllers I find the comments that the inclusion of motion controlls on next generation consoles "Ruins" gaming to be remarkably moronic ...
With that said, the biggest problem for Microsoft and Sony will be that they will be creating a first generation motion contoller while Nintendo will be working on their third-iteration ... On top of this, Nintendo will also have access to several of the most talented designers in the world who will have completed several games using their first and second iteration controllers and can give feedback on how the controller should be designed.
This may not seem like that major of an advantage, but Nintendo may be able to outshine Microsoft and Sony simply because they have far more experience in developing motion controlls and unconventional user interfaces.
