Well there are loads of screenshots on the web now.
Project Gotham Racing 3, I have to agree is going to be the best graphical racing games when it comes out.
The buildings do indeed look real, and one bridge for example which you'll be racing across in one map is made up of 900,000 polys.
The cars are made up of 600,000 for the outside, and I think 600,000 for the interior too.
Now thats mesmirising!
As I've said before, it wont just be the graphics that will push these games, but the gameplay, the advanced A.I, the advanced physics, and the advanced effects, like motion blur, camera focus, etc.