John Cazale only appeared in five movies. All of them were seminal, amazing films. He never made a bad movie or even so much as a simply decent movie. He was in Dog Day Afternoon, The Conversation, The Deer Hunter, and The Godfather I and II. Every single performance is riveting, scene stealing and Oscar quality.
Oddly, in forty percent of his roles he was named Stan.
He died of bone cancer soon after filming for The Deer Hunter finished. At the time he was engaged to Meryl Streep.
Obviously it is hard to forecast what kind of work he might have done in the future but I think it's safe to bet he would have put in some solid work in the eighties. He probably could've at least scored a supporting role in Cruising since he and Al Pacino were extremely good friends. Welcome to the Movie Goer Hall of Fame, John Cazale.