Just depends what kind of racer you're into. More fast-paced less realistic games like Burnout, Mario Kart, more street racing arcade games like Midnight CLub and Need For Speed, more realistic racers like Forza Motorsport or Gran Turismo, or maybe even hybrid arcade/sim racers like Grid and Forza Horizon. There's something for everyone in the racing genre.
I prefer simulation racing over arcade(though I fukk with both) so Forza Motorsport and Horizon are the best racing games ever to me.
BUUUT Burnout is stupid fun. 3 might've been my favorite racer at that point in time, or atleast up there since I hadn't found the magic of Forza at that time, but still played Gran Turismo. Paradise was an awesome take on Burnout. Never even thought to make it open world like that.