I got GTR free with some hardware. Far too simulatory for my liking. I'd say Grid, like Gotham and Forza, are just right for my taste. The best thing is the variety of styles of driving, it keeps it more interesting.
I find it more fun with all driving aids off, but i'm still running in 'Auto' gears for now. My only beef with the game is the guy that pops up on the radio every-ten-****ing-seconds