I've googled more ideas. They could also improve on:
More photo-realistic in motion
More photo realistic in general
Physics update
Bikes
a whole host of racing types/genres
rikshaws ( I googled races I think, and somehow ended there... :lol )
*Rewind*
( ... some people I hear want it)
*virtual cities to drive around
*garage in Home (?)
* Pink slip races (from this very thread actually)
* Full on livery editor
* build your own car from scratch, shape it, design it, test it, run it, wind tunnel etc
Oh theres more, but that reminds me. Wind tunnel, whatever happened to that?