Bah, the other thing everyone seems to be forgetting is that the cager doesn't give a crap about bumps in the road, gritty surfaces, etc.
The R1 Rider isn't riding at race pace no, but then again racers on the road don't race at pace all the time either. It would be suicide. The ring is fairly bumpy and dirty, yeah the Porsche will lead into the corners, basically it doesn't have to slow down as much or as early.
Again Jvue, I disagree, I think most true race cars will hand even Rossi his ass on his best day. With a little research we should be able to find European Touring Car lap times and compare with a MotoGP, they might share some circuits and the Touring cars are full bodied "Stock" cars. But hell I could be wrong...