I also strongly agree that Burnout 3: Takedown and Burnout Revenge are the best in the series, the most focused and polished… Burnout Paradise is OK but lacks something those other two have.
Whenever I think about Burnout Paradise I think about somebody (I think it was Yahtzee) describing the world of Burnout Paradise as a post apocalyptic nightmare world where cars have taken over, and one lone human hides out in his radio station broadcasting desperately to a murderous mechanical audience.