I don't play too many racing games compared to say, FPS. But if it's fun I'll play it, Flatout is one of my favourite games, it's heavily physics based, but that's what makes it fun, you can smash the scenery to hell, crashes are great fun, and every race is different because of the super accurate physics deteriorating the track each lap. I wish they'd do a motocross game like Flatout, MX vs ATV is ok but with all of Flatouts cool physics it would be mad, kinda slow things down a lot so we can play with the physics properly. Imagine knocking down a billboard so it leans against a barn, then using it as a ramp, a game like that would keep me occupied for months.
I like RR because it's really about getting those drifts perfect, like turning in early and sweeping around corners at mad speeds and maintaining the speed all the time. RR looks impressive too, it's amazing to watch someone really play it, like someone who knows the track perfectly, it's just a skillful game and totally in your face with the music and everything.
On the other hand, NFS is a bit too involved for my liking, PGR is the same - Burnout is fun, but really the new burnout games are getting dull. I liked the first 2 burnout games on XBox, before EA got their greasy hands all over them.