thats what i thought...the mistake was “creating” a story...where as the first 2 were obviously based on a real life story line...maybe should have loosely traced the Gambino family up to the John Gotti years...some thing along those lines...
Alternatively, as PAR35 suggested, do a Soprano ending and have Michael whacked at the end of Godfather 2. We had the seen the complete corruption of Michael through the first two movies and by the end of Godfather 2, he had alienated everyone in his life that previously mattered. Have Al Neri, probably the only guy who Michael still trusted, betray Michael and whack him. Not that different than what Gotti did to seize control of the Gambino Family, although I don't think that Paul Castellano trusted Gotti. It would have been a good conclusion in my opinion to show the ultimate hopelessness of that lifestyle.
Actually, the movie’s plot lines echo the Sicilian Mafia’s money laundering in the 1980’s.