According to the not-many texts I rode about real life mob, Charlie Lucky Luciano was the most powerful, but for a short time.
From 1931 to 1936, he lived as a king, everybody wanted to get in touch with him so much that he got reclusive, spending the whole days in his hotel room and just going out at night.
My opinion is that from the moment Charlie killed Maranzano until the day he went in jail he got the most power a mobster has ever had.