Even after release, this game is still awesome.
Graphics: 10/10
The main attraction for the game is the graphics. This maxed out the PS2's capabilities. This was the main reason most other people play racing games. I like:
Gameplay: 9.5/10
Sure, the diverse amount of races in Simulation Mode make the game shine, the Arcade Mode is the best. For each new car you purchase, the car and all colors are added, totaling 700+!
Longetivity: 10/10
Just beating the game is a b#%&#! I'm only about halfway through and unlocked 601(exactly) cars, all tracks, and most licenses. The endurance races require you to drive or "direct" in B-Spec mode for a period of time. This is why I want a cheating device to cut time.
Track Variations: 9/10
Tracks are separated in 4 categories: real circuits, circuits unique to Gran Turismo, city courses, and Dirt and Snow. I only find city circuits most interesting because it has my all time favorite course: Special Stage Route 5.
Car Choice: 10/10
Though I'm tired of 10's, the car's succeed in variety. From the Ford Model T to the original Nike One, the diverse amount of cars is just... awesome.
Rent or Buy?
If you don't have the $10, rent it. When you have the money, get it. You'll never regret it. Until you sell it and realize it was important.
In conclusion, this really is the best game I've ever played.