Of course, Eastwood turned it down. "This was when they first started to think about making it. I was like, 'Superman? Nah, nah, that's not for me.' Not that there's anything wrong with it," the actor disclosed. "It's for somebody, but not me." In the same interview he also confirms that he was close to becoming the first American James Bond in the 007 series.
Eastwood eschewed the super heroic roles to play men that were more down-to-Earth than the Man of Steel. Eastwood as Superman almost certainly would've meant that a different actress would've been cast as Lois Lane. Margot Kidder was cast due to her chemistry with Christopher Reeve, and I just can't see Kidder and Eastwood's dynamic playing out the same way. The biggest missed opportunity in all of this is how cool would it have been to see Eastwood as Supes face off against Gene Hackman as Lex Luthor.