Who is the best racing driver of all time?

It's a question that's been around since the birth of motorsport, and one that will likely be debated through the end of time. Who is the best racing driver of all time? Directly comparing drivers from NASCAR, F1, IndyCar or any other form of racing in their own machines wouldn't be fair, but what if we could take top runners from all walks of motorsport, and put them head-to-head in the exact same cars? Well, it happened once, but it didn't exactly turn out the way it intended. This is IROC: the International Race of Champions.