Larry Niven answered this question decades ago (”Man of Steel, Woman of Kleenex”). Superman, despite his human appearance is an alien species. A Homo Sapiens woman would be as attractive to him as a chimpanzee would be to a Homo Sapies. Wrong phermones, among other things.
Now it is possible that given a long-enough isolation from his own kind, Superman might develop . . . ah . . . outlets. But it would be as “natural” as a human male developing a crush on a chimp. Not that there is anything wrong with that — as they would say on Seinfield.
I dunno - it seems like proof on the other side would be Captain Kirk - for whom other-speciesness seems to have made him even hornier.