As others have said, PGR2 was like a sim lite game. If Forza or GT4 is a 10 and NFSU is a 1 on the sim continuum, then I'd say PGR2 is around 6-6.5. Each car had a fairly distinctive feel and weight. As well, each car had fairly unique handling traits.
For me, there was enough arcade in PGR2 to make it fun to play, and not so bad to pick up for a noob. OTOH, to master the platinum levels you had to maintain pretty strict lines on many of the courses.
Apparently, PGR3 expands on the uniqueness of each car even more. I just hope they haven't screwed the pooch on the Kudos system. I wish that they had a better car selection, but I understand the decision. Hopefully, once Bizarre gets a better handle on the 360, they'll expand PGR4 in much the same fashion that they did going from PGR1 -> PGR2.