Vito Corleone is a composite of real-life Dons. He's like Joe Profaci (olive oil king), Joe Bonanno (bringing his son along in the business, betrayed by an underboss), Carlo Gambino (never did time in jail), Salvatore Maranzano (defeated a rival boss by having him killed in a restaurant). But Vito's most like Frank Costello, "the Prime Minister," who had the gambling and the unions, was all-powerful politically, had all the judges in NY in his pocket, eschewed drugs, and retired after an unsuccessful assassination attempt.
Here is a rundown of other characters in the Trilogy who do--and don't fit "real life":

Close Fit:

Johnny Fontane = Frank Sinatra: Washed-up, teen-idol crooner with fealty to the Mob; role in war movie puts him back on top; sluttish, movie-star ex-wife.
Hyman Roth = Meyer Lansky: Jewish adviser to Mafia; “always makes money for his partners”; tight with president of Cuba; started out as a truck mechanic and got connected during Prohibition; fled to Israel and South America to escape Justice Dept.
Moe Green = Bugsy Siegel: Pal of Jewish adviser to Mob; “headstrong, talking loud, saying stupid things”; “city he invented was Las Vegas”; “someone put a bullet in his eye.”
Johnny Ola = Vincent (Jimmy Blue Eyes) Alo: “Sicilian messenger boy” to Lansky [N.B.: Name is an anagram.]
Joey Zasa = Joe Columbo/John Gotti: Meucci Society = Italian-American Civil Rights League; “Best-Dressed Mobster”; publicity hound; shot at Italian-American event.
Rosato Brothers = Gallo Brothers: Renegade faction in Mob family declares war on Don (Joe Profaci); Joey Gallo recruits blacks and Hispanics while in jail; “leave the gambling for last.” [N.B.: Eldest brother Larry was garroted in the back of a Brooklyn bar after-hours in 1960 and was saved by a NYC cop who happened by—the basis of the Frank Pentangeli-Rosato Brothers scene, but with roles reversed.]

Stretch Fit:

Emilio Barzini = Vito Genovese: Tried to kill rival to become Capo di Tutti Capi; attempted to make move on drugs at gangster convention (Apalachin).
Frankie Pentangeli = Joe Magliocco: Weak successor to strong Don (Profaci); beleaguered by rival faction.
Peter Clemenza = Frank Labruzzo (Bonanno Family): Top capo to Don (Bonanno) stayed loyal to son of Don (Bill Bonanno) during gang war; philosophical bent. [N.B.: Richard Castellano played Labruzzo in the TV movie, “Honor Thy Father.”]
Sal Tessio = Gaspar Di Gregorio (Bonanno Family): Top capo to Don (Bonanno) betrayed Don and son by siding with rival Don (Stefano Maggaddino) in return for being named head of his own family.
Fredo Corleone = Thomas Gambino: Weak son of Capo di Tutti Capi is passed over, given “legit” businesses to run.
Luca Brasi = Willie Moretti: Legendary strong-armer; “can do a job of murder all by himself”; “most valued friend” of Joe Bonanno and other Mob bosses; killed by the Mob (probably Vito Genovese).

No Fit:

Michael Corleone. No son ever succeeded and surpassed his father as Don. [N.B.: The two who tried--Bill Bonanno and Junior Gotti--both wound up in jail.]
Tom Hagen. No non-Italian has ever served, officially, as a Family’s consigliere.