Don't know Turnbull I reckon II brought closure, in the platinum standards set by GF and II but you are correct, III was already disadvantaged before a shot was fired, by having Godfather in it's title which obviously elicited the high expectations

Crime does pay for some!
Vito's life was equally reprehensible but I reckon, he is seen through rose-colored glasses He too was a cold blooded murderer

Also I reckon he neglected his blood family, leaving all sorts of needless problems for Michael