I got PG2 for Xbox a few weeks ago after enjoying the single player of PG1. Some say that after a while the game becomes repetitive but something prevents that from happening. The graphics are great, but that's not it, it's that the graphics start looking realistic. There are points (though not all the time) when I can swear that I'm looking at a real picture you'd see on TV or at least at something taken from a 3D cinematic movie. I have no doubt, that the fact that the game is at a low resolution and utilizes AA to achieve high detail instead, contributes to the realistic picture but also it's something that conveys the atmosphere of really driving through a city.
My favorite is driving through Florence at night in a car from the roadster series.
Another thing that adds to the game's longevity is that there are so many cars arranged in series and each series which is comprised of about 7-9 races. Since you can't drive a car from one series in another you constantly have to get used to different cars, so instead of driving better and better car you just drive different cars.
I'm not a big fan of racing games but this game is one of my favorites for the box (after Halo for multiplayer and Crimson Skies for single-player)
Got a nice overclocked overvolted system to keep you warm at night? That's great. Guess I'll have to settle for a woman...