'Godfather' Actor -- Coppola Is Dead Wrong About 'Godfather 2'

Francis Ford Coppola didn't just stun his fans when he told TMZ he only should have made ONE "Godfather" movie ... he also shocked the hell out of one of the actors who starred in "Part II."

"TMZ Live" spoke with Frank Sivero -- who played Don Vito's consigliere Genco Abbandando in the flick that's widely regarded as the greatest sequel of all time.

Sivero tells us he regards the ACADEMY AWARD winning movie as a "masterpiece" -- and says he's completely baffled as to why Coppola would ever make such an outrageous claim.

You broke our heart, Francis.