To elaborate, PGR4 lacks the depth and realism that makes the Forza and Gran Turismo games so excellent. The 'kudos' points system is pretty uninteresting during the career mode, and it simply doesn't feel as rewarding as it should. The racing segments are solid enough, but completely standard by this point. The many different types of races all feel lackluster after a few hours of gameplay, and there's nothing else compelling enough to keep you playing.
Bottom line, this game is just not that much fun for me. The career mode isn't nearly as enjoyable as it should be, and considering the wealth of other Xbox 360 racers out there, I can't think of too many reasons to play this one.
Tight gameplay, beautiful graphics, and excellent sound effects make this a moderately decent game for fans of the genre, but it's nothing great or revolutionary. I got Project Gotham Racing 4 at my local video game store for only $4, so with that in mind, I might recommend this game to racing fans more than I normally would.