GT4 is my favorite racing game ever, solid control, graphics and game play.
Basically the graphics are solid for game of this age, they look sharp, shinny and the interface looks nice too.
Secondly the gameplay is great, as a single player game you feel like your in a whole world inside this game, you can go places, check things out, race here buy a car there, it really is like a roleplaying game in some ways. But not only the freedom the game has makes it great, there are all of your races which are well ballanced and then there are licences which you have to go for, they are great fun too, not just to get them but then to try to finish each challenge with a high enough score for the gold medal.
thirdly the feel of this game as in the control is as solid as. I have never felt so at home driving a car than in this game it just feels right.
My advice is go get this game if you are looking for the best driving game available on PS2.