I'm not surprised many people name Carlo Gambino and I know why people put him there. However, he was seen as a weak man in the eyes of many in that world. "A squirrel of a man" as Joe Bonanno put it and many seemed to echo that. One of them being John Gotti who was overheard on tape calling him a "rat motherfucker". Then he certainly didn't help his legacy by picking Paul Castellano as his successor, one of the worst decisions a Cosa Nostra boss has ever made. Gambino was surely an intelligent man, but he was far from being tough. He was the type of guy who needed to hide behind his guys. Yes, he did isolate himself and he's one of the very few bosses who truly succeeded in the world of organized crime. However, that alone is not enough to make him a great Cosa Nostra boss.