I never considered myself to me a racing game fan. Even some of my favorite games have racing sequences and I hate them. But Burnout Paradise is one of my favorite games on the PS3.
Gran Turismo 5 is definately the most realistic but my most fun was Burnout Paradise with friends. 6 of us just crashing, smashing and bashing each other
Simulation: GT5. It's not even close. When playing it with a wheel it's true bliss. Unfortunately the standard cars, lack of tracks and dull single player campaign make it slightly disappointed. To me GT5 as a simulation it's a 10/10 but as a game it's a 7/10.
Arcade: Burnout Paradise. One of the best games of this gen, especially the online component that offered a true sandbox for us to play. I spent hours just playing around with 7 other players. I wish Criterion implement some of Burnout Paradise in the next Need for Speed game.