Heath Ledger was perfect as the Joker, despite fan reactions to his casting, and Michael Keaton was a great Batman, despite fan reactions to his casting. Sometimes Hollywood gets these sort of bold, creative decisions right, and the pay offs are enormous.
But then sometimes, some lunatic with a casting couch decides that the best way to make a superhero film is to ignore all logic and cast actors wholly unsuitable to the roles, with the faint expectation that somehow, it would all come off. Thankfully, the flat-out ludicrous casting dodged bullets below are just that, and we were never treated to the sight of any of this motley crew in the roles that could have been theirs.
First up, an immediate rule breaker...
He made Batman, and it was great. He then made Batman Returns, and it was also great. But had Tim Burton made Superman, we would have had another terrible Superman movie, which would have pretty much destroyed everything fans knew and loved about the Superman property.
Regardless of what the plot was to be, or the casting decision behind the film - which for the record were diabolical with Nic Cage as Supes, Chris Rock as Jimmy Olsen, Tim Allen as Brainiac and Kevin Spacey as Lex Luthor (the only sensible decision of the entire ridiculous project) - it was Burton's influence that would have been worst.
I'm a big fan of Burton - I will apologise for his terrible work because of his commitment to his artistic vision, but even I recognise that his idiosyncratic imagination would have ruined Superman's wholesome image, even if Smith's script might have made a good movie (albeit without Jon Peters' ludicrous suggestions.)