First off i have two things to say.
1,forza 3 was the worst forza
2.microsoft arent doing themselves or anybody else any favours.
Forza 4 is great improvement over its predecessor,big time better graphics,the cars seem to have more snap and theres more to the game than just going around in circles,which was all there really was to do in forza 3.
What really broke forza 3 was that stupid triangle,4 has the triangle but luckily it isnt bugged,you will only get it if you have done something wrong.
Also rivals mode is a revelation,you can still participate even if you dont have gold which i see as an act of good faith from turn 10..
The game is just better in every single way to its predecessor.The only problem i have is that it could have done with more tracks and a lot of stuff isnt available if you dont have gold,buts thats more to do with microsoft than turn 10.
Nearly forgot,you cant get the maximum 1000 gamerscore if you dont have kinect,seriously,microsoft would want to learn to keep its nose out.