I'll respond to a few concerns.
FPS: No brainer.
RTS: As a pointing device, the controller is BETTER than a mouse. It can pick up lateral movements in 3D space as well as tilts, that'd let you do shit you wouldn't even think about in a traditional RTS.
Additionally, for people bitching about keys, the first thing I imagined was a small num-pad add-on to the remote that gave the user all of the hotkeys they'd need.
I'd hope something more intuitive could be accomplished, since if no one gets hotkeys then it's a level playing field.
Racing: Anyone else see the steering wheel photoshop mockup? Imagine if that thing drew some power from the remote to offer decent force feedback? Or also had a simple plastic setting stand behind it with a bearing that let you rotate the whole thing easily. Then you'd get your tactile response and feedback for minimal manufacturing cost. It'd be easy to do.
Sports: Just do the motion instead of hit the button, easy.
Rail Shooters: Easy answer. Far superior to pads
Rhythm games I think are among the most likely to improve. Suddenly any drumming game, beatmania (see numpad), and a number of visualizer games like Rez and Freq/Amplitude would be great.
RPGs: the controller proves most RPGs could be played with one hand anyway. I'd love to be able to eat a sandwich while playing FF.
Any takers for telling me I'm wrong?