In the first one, it has to be Brando. He just makes that film larger than life and as iconic as his performance has become, the substance is there. It's simply a pleasure to see him do his thing.

John Cazale is often underrated, and such is the case in Part II. He brings a humanity and a sympathetic side in Fredo's plight, and his performance may even justify Fredo being shunned and lashing out. Fantastic.

As for Part III...I'll say this, Eli Wallach turned in the worst. Ok, maybe Sofia. But Eli wins out because he's a legit actor and that garbling mess of a performance was terrible.