Today's sportbikes are blindingly fast and handle on par with full-on race bikes of years past. Today's high-end sports cars are also stunning in the performance department. So if you took a Ducati 1098S and put it up against a Nissan GT-R, who would win?
The answer ultimately depends upon the racetrack. Cars make up a lot of ground in corners, where they benefit from a larger contact patch between tire and road. Bikes pull away quickly on the straights, with acceleration that most cars can't touch. On a high speed oval, like the Indianapolis Motor Speedway, a bike may very well be the quickest option. On a road course with limited straights and a few tight corners, it's advantage, car.
Want some proof? Check out this video posted at RideLust.