This one is a little bit of a stretch. Sam Waterston played Abraham Lincoln in the 1988 mini-series "Gore Vidal's LINCOLN". Then, he played Lincoln in voice-over only for the 1990 Ken Burns PBS television documentary THE CIVIL WAR.
Joseph Crehan played General Ulysses S. Grant in nine different westerns, starting with Cecil B. DeMille's UNION PACIFIC (1939) and including the Errol Flynn film THEY DIED WITH THEIR BOOKS ON (1941) and Fredric March's THE ADVENTURES OF MARK TWAIN (1944).
William Jordan played John F. Kennedy in the little seen 1977 Larry Cohen film THE PRIVATE FILES OF J. EDGAR HOOVER (score by Miklos Rozsa) and then reprised the role in the more widely seen NBC television mini-series on Dr. Martin Luther King, 1978's KING, starring Paul Winfield.
Michael Sheen first played British Prime Minister Tony Blair in Stephen Frears' 2003 television film THE DEAL, about Blair's friendship and rivalry with his contemporary, Gordon Brown. Frears used him again in 2006's THE QUEEN, with the tile role played by Helen Mirren. And most recently, in 2010, Sheen played Blair in the HBO film THE SPECIAL RELATIONSHIP, about Blair's dealings with Bill Clinton and George W. Bush.
Michael Sheard portrayed Adolf Hitler five times in his career, in Rogue Male (1976), The Tomorrow People (1978), The Dirty Dozen: Next Mission (1985), Indiana Jones and the Last Crusade (1989) and the documentary Secret History: Hitler of the Andes (2003).
He also portrayed Heinrich Himmler three times, in The Death of Adolf Hitler (1973), The Bunker (1981) and Space (1985).
Surely the most prolific is Martin Kosleck, who played Goebbels in many features and short subjects. Second to Kosleck is Bobby "Moses supposes his roses are toeses" Watson, who played Hitler in many films including CITIZEN KANE and the two Hal Roach axis burlesques THE DEVIL WITH HITLER and THAT NAZI NUISANCE. No joke.
Although only identified as "CINCPAC II" in the credits, Henry Fonda is basically playing Admiral Chester Nimitz in "In Harms Way". A decade later he was Nimitz in "Midway."
Howard Da Silva after playing Benjamin Franklin in "1776" did return to the role again for the National Parks Service film shown for 20 years at the Franklin Court Museum, "Ben Franklin: Portrait Of A Family."
And while this is stage not film, I should take note that after playing Jefferson on Broadway (and the film) of "1776", Ken Howard did play Jefferson again (and a number of other presidents) in the infamous flop musical "1600 Pennsylvania Avenue".
For the opponent in later film, there's John Gielgud playing Cassius in the 1953 version of "Julius Caesar" and then playing Caesar himself in the 1970 version.
This one is a little bit of a stretch. Sam Waterston played Abraham Lincoln in the 1988 mini-series "Gore Vidal's LINCOLN". Then, he played Lincoln in voice-over only for the 1990 Ken Burns PBS television documentary THE CIVIL WAR.
Related to that would be Gary Oldman after playing Lee Harvey Oswald in "JFK" doing Oswald's voice for readings from his diaries for the 1993 documentary "Who Was Lee Harvey Oswald?" (which took a different conclusion from Stone)
Bobby Kennedy has been portrayed by an actor named James F. Kelly in six different productions:
"Jacqueline Bouvier Kennedy" (1981-Jaclyn Smith as Jackie, James Franciscus as JFK) "Prince Jack" (1984) "LBJ-The Early Years" (1986) "J. Edgar Hoover" (1987) "Onassis: The Richest Man In The World" (1988) "Dark Skies" (1996 TV Series)
And he also played JFK in the 1992 miniseries "Sinatra"
Ernest Borgnine was J. Edgar Hoover twice.
"Blood Feud-Kennedy vs. Hoffa" (1983) "Hoover" (2000) (a one-man performance)
William Powell played Florenz Ziegfeld in MGM's 1936 biography THE GREAT ZIEGFELD, and he also played the role (from a heavenly vantage point and in Technicolor) in MGM's 1946 production, ZIEGFELD FOLLIES.
