Now here's how I see it. Vito was a noble man brought into a life by a few circumstances. The movie (unlike the book where he is said to have murdered to cause fear (the union cheif working on fontane's movie))portrays VC as a great man, which indeed he was, patient, wise, thoughtful, compassionate, amicable. He had all the qualities that the classic leader should.

Michael on the other had had many of these qualities, however he does get tyranical in GF I to a certain degree. He although many of the qualities of Vincent, does not have the same qualities of fairness or justice that VC has, since he did kill his own brother after being convinced of his total betrayal. He has by GF III become a man who has matured with age, gotten out of his bad habits. Still he allows the family to fall out of Legitamacy and back into the cycle under Vincent's tutiledge.

Vincent on the other hand has all the qualities of the 3 brothers. He has the thoughtfulness of Michael and all the other mental characteristics that made him great. He has the strength and good looks of Sonny as well as the passion and anger. He likewise has the charm and heart of Fredo. He is in many sense a different incarnation of Vito, in some ways.