If we include PC, Trackmania, no game comes even close to the number of tracks that game has thanks to an amazing track builder inbuilt, not even Mario Kart tracks get anywhere near as insane as some of the best tracks I've seen built in this game. I played a puzzle track that needed some insane stunts and amazing driving to complete, that was 2 hours long, and this server had another 100 or so tracks all like that.
If not PC or basically run by the fans, my favourite racing games are probably the Burnout series and the Mario Kart series, both for their differing takes on how to fuck up someone else at high speed.