Cristina, I compressed your quote here because the above says it all for me. III contains most of the elements of greatness in the earlier films. But the plot falls apart soon after Vincent shoots the two intruders. It never answers some fundamental questions:

What is Immobiliare? Why does Michael need to dominate it in order to be legitimate, if he's already a Papal Knight and benefactor of Sicily? Why did Gilday doublecross Michael? Who is Lucchese? Why is he out to get Michael? Where did Altobello come from? Why is he out to get Michael? When and how did Michael resolve his conflict with Anthony?

An astute friend, after seeing III for the first time, observed that "there must be ten hours of plot and connective tissue on the cutting room floors."