The reason you're wrong is because the semantics of C restrict what compilers can do. Humans know the actual semantics they require, and thus, when writing assembly language, can retain only those semantics, dropping everything else. Thus, "ingenuity" as you put it is a real advantage that humans actually posses over what a compiler can do—even if we gave that compiler an infinite amount of time.

This is quite unlike chess, where the rules are known up front, and are the same for both the computer and the human.