I'm putting up with Forza2. PGR3 I loved, can't tell if it's because it was a launch title or the fact that the 360 was new, but I certainly had more anticipation in waiting for the online games with OcUK'ers on an evening that I am with Forza2.
Graphics wise, F2 is definately better, but PGR3 seemed more of a great arcade racer, immediate hands on, lots of laughs, fun fun fun, where as F2 seems more of a thinking mans game.
Between the 2 I'd have to say that graphically and aurally, F2 wins hands down. But for overall enjoyment, PGR3 still beats the majority of racers. Definately benchmark material that one.