Why no one mention Forza 2, its awesome (I am waiting for my copy to arrive).
If you have X360, go try the demo, and if you like it, you like full even more, because for example, the damage in demo is not simulation. In demo if you hit head-on to wall 250 KM/H only change is cosmetic, but in full game, you can choose different damage types, and when on simulation, car will start behaving like it should be, when damaged.
Ohh....i want to make 1000hp car already,can't wait!