1970s
Caan returned to the small screen with the TV movie Brian's Song (1971), playing dying football player Brian Piccolo, opposite Billy Dee Williams. Caan did not want to return to television and turned down the role several times, but changed his mind after reading the script. The film was a huge critical success and Caan's performance earned him an Emmy nomination. He got a deal to make a film and agreed to be in T.R. Baskin.
The following year, Coppola cast him as the short-tempered Sonny Corleone in The Godfather. Originally, Caan was cast as Michael Corleone (Sonny's youngest brother); both Coppola and Caan demanded that this role be played by Al Pacino, so Caan could play Sonny instead. Robert De Niro was also considered to play Sonny. Although another actor, Carmine Caridi, was already signed to play Sonny, the studio eventually insisted on having Caan, so he remained in the production. Caan was nominated for an Academy Award for Best Supporting Actor for his performance in the film, along with co-stars Robert Duvall and Pacino. Caan was closely identified with the role for years afterward: "They called me a wiseguy. I won Italian of the Year twice in New York, and I'm Jewish, not Italian.... I was denied in a country club once. Oh yeah, the guy sat in front of the board, and he says, 'No, no, he's a wiseguy, been downtown. He's a made guy.' I thought, What? Are you out of your mind?"
Caan was now established as a leading movie star. He was in a road movie, Slither (1973), based on a script by W. D. Richter; and a romantic comedy with Marsha Mason, Cinderella Liberty (1973), directed by Mark Rydell. He received good reviews for playing the title role in The Gambler (1974), based on a script by James Toback originally written for Robert De Niro, and directed by Karel Reisz. More popular at the box office was the action comedy Freebie and the Bean (1974) with Alan Arkin.
Caan reprised his role as Sonny Corleone for a flashback scene in The Godfather Part II (1974). He had a hit with Funny Lady (1975) playing Billy Rose opposite Barbra Streisand's Fanny Brice. Caan starred in two action films, Norman Jewison's Rollerball (1975) as a star athlete of a deadly extreme sport, and Sam Peckinpah's The Killer Elite (1975). Both were popular, though Caan hated Elite. He made a cameo in Mel Brooks' Silent Movie (1976), and tried comedy with Rydell's Harry and Walter Go to New York (1976). Caan was so unhappy with the latter he sacked his management. He said he did not want to make Elite or Harry but "people kept telling me I had to be commercial."
Caan was one of many stars in the war film A Bridge Too Far (1977). He had a change of pace when he went to France to make Another Man, Another Chance (1977) for director Claude Lelouch alongside Geneviève Bujold, which Caan did for "peanuts" and "loved" the experience.
Back in the United States, Caan made a modern-day Western, Comes a Horseman (1978), with Jane Fonda for director Alan J. Pakula. He was reunited with Marsha Mason in the film adaptation of Neil Simon's autobiographical Chapter Two (1979). Caan later said he only did the film for the money as he was trying to raise money for his directorial debut, but it was a success at the box office.
In 1978, Caan directed Hide in Plain Sight, a film about a father searching for his children, who were lost in the Witness Protection Program. Despite critical praise, the film was only moderately successful with the public.
During Caan's peak years of stardom, he rejected a series of starring roles that proved to be successes for other actors, in films including M*A*S*H, The French Connection, One Flew Over the Cuckoo's Nest, Close Encounters of the Third Kind, Kramer vs. Kramer ("it was such middle class bourgeois baloney"), Apocalypse Now (because Coppola "mentioned something about 16 weeks in the Philippine jungles"), Blade Runner, Love Story, and Superman ("I didn't want to wear the cape".). In 1977, Caan rated several of his movies out of ten – The Godfather (10), Freebie and the Bean (4), Cinderella Liberty (8), The Gambler (8), Funny Lady (9), Rollerball (8), The Killer Elite (5), Harry and Walter Go to New York (0), Slither (4), A Bridge Too Far (7), and Another Man Another Chance (10). He also liked his performances in The Rain People and Thief.