Laurence Olivier was considered for the role of Vito Corleone before Brando was cast. Hard to imagine, and of course it would have been a very different film, but I think he could have pulled it off. Someone--and it would have to be a first-rate actor, likely British, not some impressionist/comic--should make a short film of what might have been. Maybe just that first scene with Bonasera the undertaker.