Prime Mover is my pick as well! What a nice underrated little game that one is...
Top-Down, has to be ATR or MicroMachines. MicroMachines excelled in 2P mode. But what category would Skidmarks fall into? I like that one as well. I always think of it as a super super "super off-road" :P
Pseudo 3D, Lotus 2 no question. Second place for Crazy Cars III/Lamborghini Challenge
And 3D racing, F1GP. Stunt Car Racer was fun but too dull sometimes, and teh CPU was unfairly unfair.