1) Muhammad Ali
Of all of the names on this list, the late, great Muhammad Ali has got to be the least likely contender to play Superman. Apart from his obvious differences from the usual look of the character, he wasn’t even an actor.
Early on in the casting process for the 1978 movie though, Salkin briefly considered putting the boxing champ in the spandex suit. Casting a black man as Supes would be a surprising move now, let alone in the 1970s, so kudos to the guy for being so open-minded.
In the end, Ali wasn’t actually formally approached for the part, so we’ll never know if he would have been interested. Funnily enough, though, he would be immortalized in Superman comic Superman vs. Muhammad Ali the very year that the movie was released.