If Don Corleone did not choose Michael Corleone to become Boss of the Corleone Family, who do you think would have been a good choice for Don Corleone to choose as Boss of the Corleone Family?

I think, if Don Corleone did not choose Michael to become Boss of the Corleone Family, he could have chosen Sal Tessio. Sal was the smartest of the Corleone Family's most powerful Caporegimes, and without the help of Don Corleone, Michael would have never known that Sal was conspiring with Don Barzini to murder him.