there are many people who are very intelligent, far more so than Einstein was, but aren't inclined to originality
I have a physics Ph.D. friend who is quite brilliant himself, and when I asked him about Einstein he said something like Einstein had a particularly good, intuitive grasp of physics principles in a way most people weren't capable of. Actually I don't remember if this was Feynman or Einstein; I was asking him about the two, and basically he said that each of these people had some uncanny ability.
Daniel Tamment http://en.wikipedia.org/wiki/Daniel_Tammet isn't insanely intelligent but due to a different brain structure, has a supernormal memory, which makes him appear abnormally intelligent and creative. When he talks about shapes of numbers you can say he is particularly creative, but I find it impossible to dispute that this comes as a result of a brain anomaly he was born with.
Feynman also had incredible facility with calculation: he was one of the first Putnam fellows. He left the exam early!