Off the top of my head...
Lucky Luciano
Frank Costello
Tony Accardo
Carlo Gambino
Tommy Lucchese
Gerry Catena
Tony Corallo
Frank Tieri
Tony Salerno
Vincent Gigante
Angelo Bruno
Jack Tocco
I will add some to this lost:
Joe Bonanno: a lesser version of Frank Costello as it comes to business smarts, became the youngest boss ever of one of the most powerful crime families in the United States
Paul Ricca: ran the Outfit, and possibly its ultimate top boss
Joe Massino: brought the Bonannos back from ruins, one of the few who felt Pistone was no good, outsmarted the cops for a long time
Santo Trafficante: ran Florida for 40 years and was after Lansky the most powerful mobster in Cuba
Carlos Marcello: ran Louisiana for 50 years and could have organized the JFK assassination
Johnny Torrio: laid the foundation of the Outfit, became a senior advisor to Lucky Luciano
Vincent Alo: business partner to Meyer Lansky for 50 years
Russel Bufalino: ran a tight-knit family but was a very influential crime figure, organized the killing of Jimmy Hoffa
Frank Rosenthal: probably one of the best gamblers ever, great business sense and very innovative when it came to running a casino
Moe Dalitz: mister Las Vegas himself, managed to become one of Nevada's most respected businessmen while being a gangster
Anthony Scotto: became a union president, had many powerful political connections while secretely being caporegime in the Gambino crime family
John Roselli: had powerful political connections, worked with the CIA on the plot to kill Castro and could have been involved in the assassination of JFK
Murray Humpreys: one of the most powerful figures in the Outfit while not even being an Italian