redford would have been hopeless. He is like Warren beatty - wooden. Both preen in front of the camera because they were lucky to win the lottery at birth for above average looks.
Al got over the top in most of his stuff. Still, he was quite good in the Godfather considering he was a fairly young and inexperienced actor at the time. I forget if Dog Day and Serpico came after godfather.
Pacino's first role to attract critical attention was "A Panic in Needle Park", which was a year or two earlier than the Godfather. Interesting that I was IN the actual Needle Park referenced in said film today, and the worst thing that can happen to you there today is getting run over by an aggressive UWS mom with a stroller.