Ok, I own both PGR4 & Forza 2 and have to say they are both great games, however, they are vastly different in style so all those people who are trying to compare them please stop.
Forza is first and foremost a simulation!!! Very realistic handling as anybody who has actually driven a reasonably quick car knows you can't really throw a car into a bend at 100mph, apply the brakes and expect to come out of it alive( or with the use of all your limbs), not to mention carry on driving your car with the few minor scratches it recieves after smashing into the crash barrier. So as a Simulator Forza 2 is Excellent.
But in PGR4's defence, I (and many of my friends) don't want a game thats super realistic, if Call of Duty was super realistic, the first time you get fragged with a grenade your screen shoud go black and you shouldn't be able to play the game ever again. I want a racing game that features amazing cars, great circuits and challenges, varied playing styles and fantastic graphics. PGR4 meets all these requirements, the weather effects are stunning, you can actually feel the steering become lighter as you hit standing water, the whole character of the cars & bikes change as the circuit becomes sodden with rain or frozen with ice.
We know its not super realistic but it IS SUPER FUN and not too difficult that you'll stop playng it because you keep spinning off. I give it a definitive 10 out of 10.
BUY THIS GAME!!!!!!!