A real comparison is of course impossible, but of that coterie, Kurt Gödel is a strong contender. As the original post mentions, he singlehandedly destroyed Hilbert's formalist program (which von Neumann was also working on) and von Neumann is quoted as saying he was "in a class by himself". There is the famous letter from Gödel to von Neumann which anticipates the P=NP problem by decades.

In a different era, I think Blaise Pascal is also a contender. At age 19 he invented a working mechanical calculator with a functional carry mechanism, which somehow his contemporaries failed to achieve for the next sixty years.