I don't know about anyone else but Forza 2 really doesnt seem that great from the demo. The cars felt as a friend of mine put it like "container ships" they just didnt seem to turn. Understeer is what the cars seem to suffer horribly from. Braking seemed really messed up (having to break really early for corners), as did getting into position for the corners, it was either do everything perfectly or end up off the track in the gravel. The graphics I didnt think were very good, perhaps my tft to blame, but I'd say they are only ever so slightly better then PGR3.
I'd have to say GT Concept on the PS3 is a far better game at the moment, with the assists turned off I can actually go around the track without being all over the place.
Mayby simulation racing games just arent for me anymore, but having playing gran turismo right up to the ps3 demo and then other driving games in between I don't think its my ability that is at fault