For purest who want the car as is, and love racing in city streets without city traffic and the PoPo trying to shut you down, then PGR is for you. It is the Madden of off the shelf car racing. No mods, body kits, or tuning. Pick a car, pick a color, and go racing.
The game play amoungest the four versions of PGR has not changed much, and why should it, if it isn'tr broke then don't try and fix it. From regualr straight up races, to time trials, to elimination laps, there is no more fun and variety in racing then PGR. Much like Madden ist about adding a few small minor changes and some roster updates.
My only gripe as always with PGR is that most races you have to start from the back and fight your way up. Yes, it's a challenge, but so is maintaining a lead. I'd rather be in the front and hold it then spend a lap trying to get there and another lap struggling to maintain it.
One nice thing that PGR always gives you that I have always loves is that a majority of the cars; though locked in the various career modes; are available for test driving in the freeroam; something no other racing game gives you. It's nice to get to drive the Ferrari FXX even though I haven't unlocked it yet.
In short, if you are a purest with both cars and racing then PGR4 is for you