The producer Gary Kurtz, who has died aged 78 after suffering from cancer, was one of the driving forces behind George Lucas’s 1977 blockbuster Star Wars and its masterful sequel, The Empire Strikes Back (1980). His duties extended to shooting parts of both films – directing some second-unit footage on the first, and selected scenes set on the ice planet Hoth in the sequel – during the race to finish on schedule.

But Kurtz was also one of the few dissenting voices to emerge from Lucas’s inner circle, mourning the turn that the series took after Empire towards empty, repetitive spectacle and the hawking of merchandise.

“They make three times as much on toys as they do on films,” he said in 2010. “It’s natural to make decisions that protect the toy business but that’s not the best thing for making quality films. The first film and Empire were about story and character, but I could see that George’s priorities were changing.” Producer and director parted company prior to the making of what was the third Star Wars film in the trilogy, Return of the Jedi (1983).

Kurtz subsequently sought to debunk some of the myths surrounding the creation of the Star Wars universe, qualifying Lucas’s claims that the first film was based on Akira Kurosawa’s 1958 epic The Hidden Fortress (“Not really”) and influenced by Joseph Campbell’s book on mythology, The Hero With a Thousand Faces, which he said Lucas had not read until he had almost finished writing. He called the original script “gobbledygook”, attributed its eventual lightness of tone to the uncredited co-writers Willard Huyck and Gloria Katz, and considered the CGI touchups on the 1997 re-release of the first film “annoying”.

Lucas and Kurtz were introduced to one another in the early 1970s by the film-maker Francis Ford Coppola. Kurtz warmed to Lucas’s idea for a coming-of-age story set in 60s small-town California, and produced the result, American Graffiti, in 1973. On set, he reprimanded the young Harrison Ford for drinking before a big driving scene (“Don’t show up like this again”) and observed that Lucas wasn’t exactly an actors’ director: “The actors used to joke that he never said anything but ‘do it again, faster’.” Nevertheless, Lucas and Kurtz popularised the practice on American Graffiti and Star Wars of giving the cast “points”, so that actors would receive a percentage once the films went into profit.

The success of American Graffiti did not give the pair any leverage when it came to touting Star Wars around the studios. Universal turned it down, claiming there was not a market for science fiction, and Fox agreed only after being convinced that the risk was minimal. “They just wanted to get it done and wrapped up, and it was just a kind of minor annoyance to them,” Kurtz said.

The initial outlay of prints was modest but it hardly needs saying that the film swiftly became a phenomenon, changing the shape, marketing and distribution of mainstream cinema for all time. It also made Kurtz personally wealthy: within two years of the first film’s release, he had received an estimated $25m in residuals.

Born in Los Angeles to Sarah (nee Briar), a painter and sculptor, and Eldo, a photographer, Gary was raised both there and in San Francisco. As a child, he made his own Super 8 shorts and developed a keen interest in the film industry; for one senior high school assignment, he interviewed personnel at several Hollywood studios.

He studied film at the University of Southern California and later fell in with the producer Roger Corman, working on The Terror (1963), the musical comedy Beach Ball (1965) and two 1966 westerns shot back-to-back by Monte Hellman and starring Jack Nicholson: The Shooting and Ride in the Whirlwind. Kurtz then spent two years in the Marines as a cameraman, editor and stills photographer before returning to work again with Hellman as associate producer on his road movie Two-Lane Blacktop (1971).

Following his departure from the Star Wars series, he commissioned a Ray Bradbury adaptation of the comic strip Little Nemo: Adventures in Slumberland, before leaving that project in 1984. (A different version was eventually made in 1989.) He produced The Dark Crystal (1983), an imaginative puppet adventure directed by Jim Henson, the creator of The Muppet Show, whom Kurtz had got to know when seeking advice on the character of the tiny Jedi guru Yoda in The Empire Strikes Back.

He also produced Return to Oz (1985), an audaciously twisted fantasy sequel (the film begins with Dorothy undergoing shock treatment) directed by the distinguished editor Walter Murch. Both films were box-office flops and contributed, along with a costly divorce from his first wife, Meredith Alsup, to Kurtz’s financial woes.

Citing debts of $3m, he filed for bankruptcy in 1986 in the UK, where he had settled, in north London, since making Star Wars at Elstree Studios, Borehamwood, a decade earlier.

His later films included Slipstream (1989), which reunited him with Mark Hamill, who played Luke Skywalker in Star Wars. But Kurtz’s association with one of the most influential movies of all time, and his own willingness to revisit the subject with headline-grabbing candour, meant that he was never likely to escape its shadow.

In later years, he reflected on the disproportionate emphasis that had come to be placed on a film’s opening weekend performance: “By the seventh week, American Graffiti was actually doing better business than it did in the first week, whereas if that film was released now it wouldn’t have that chance.”

He was perhaps unable to see that Star Wars, along with Hollywood’s rush to repeat the film’s success, had been the catalyst for the very changes he later bemoaned.

He is survived by his wife, Clare Gabriel, whom he married in 2003, by Tiffany and Melissa, his daughters from his first marriage, and Dylan, his son from his second marriage, to Roberta Jiminez, which also ended in divorce.

• Gary Douglas Kurtz, film producer, born 27 July 1940; died 23 September 2018