The Godfather Part III has a much worse reception than its predecessors, but it could have been much better with two casting changes. The Godfather and The Godfather Part II are considered two of the greatest movies of all time. They tell a harrowing story about the Corleone family's mafia dealings, and are full of powerhouse performances from multiple Academy Award winners. Although The Godfather Part III sees most of the original actors returning and filmmaker Francis Ford Coppola once again in the director's chair, it was not anywhere near as well received as the first two movies.
https://screenrant.com/godfather-part-3-casting-change-winona-ryder-nicolas-cage/