This might be just a coincidence, but if you look at the meanings of characters names:
Santino means "little saint" which is probably as far from his personality as possible.
Michael means "who is like God?" and indeed he could never be like God (Vito). He tries to be like his father and fails.
Good points.
I'll add another:
Connie's name (Constanzia) means "constant" or "steadfast," but she probably changes more than any other character throughout the course of the Trilogy.
