Amiga - Vroom, Supercars2, Continental Circus, RVF Honda, Buggy Boy... These are the ones I have tried since the emulator was updated with cyclone anyways.
Oh, don't forget Sonic: Drift 1 and 2 on the gamegear. Like Mariocart, but with Sonic and friends (and in terms of course complexity, probably actually more interesting than Mariocart, since it does have crude curved edges on occasion).
Super Sprint & Championship Sprint on MAME, if they are working.
Combat Cars and Micro Machines on the Megadrive.
Lotus, Lotus 2, Overdrive and Vroom! on the Amiga.
Slicks on the C64.
Plus all the other classics people have mentioned ^^^
Oh, and Virtua Racing of course. Get that to work on the GP2X and I'll give you my soul