Roger Ebert, the Chicago movie critic whose weekly TV show with crosstown rival Gene Siskel made him one of the most widely recognized and influential voices on film, died April 4 of cancer at a rehabilitation facility in Chicago. He was 70.

His longtime newspaper, the Chicago Sun-Times, reported his death.

When Mr. Ebert didn’t like a movie, he said so, sometimes sarcastically and always with passion. He and Siskel, a Chicago Tribune film critic, were accessible and entertaining, forgoing both celebrity flash and brain-busting film theory in favor of simplicity: two guys sitting in the balcony of a fake theater, talking about summer blockbusters and indie films with a passion that occasionally spilled over into personal insults.

“We were very close and friendly,” Mr. Ebert once said of his relationship with Siskel. “Except when we were fighting.”

Cancer disfigured Mr. Ebert’s face seven years ago, robbing him of his ability to speak and eat and ending his broadcast career. But he developed and maintained an outsized public presence online, writing prolifically about everything from film to politics to living with illness. It was a second act that won him a reputation for resilience and grace.

Mr. Ebert announced on his blog Tuesday night that he would take a “leave of presence” after a recurrence of cancer. “So on this day of reflection I say again, thank you for going on this journey with me,” he wrote. “I’ll see you at the movies.”

During his 46-year tenure at the Sun-Times, Mr. Ebert penned thousands of reviews examining every genre of film, from French avant-garde to Hollywood blockbusters, and in 1975 he became the first film critic to win a Pulitzer Prize. But it was through his bickering about movies onscreen with Siskel that Mr. Ebert revolutionized film criticism, pulling it off the page and into living rooms across the country.

“He legitimized the idea of talking about movies, of discussing and debating the merits of movies,” said film critic and historian Leonard Maltin. “I’m sure many people who never read a film review in a newspaper or magazine got their first taste of film criticism from watching Roger and Gene Siskel on their television show.”

The two journalists were unlikely stars. Mr. Ebert was round and short; Siskel was tall, skinny and balding; and both resembled rumpled professors in V-neck sweaters and sport coats.

As the show grew from local public television to national commercial syndication, morphing from “Opening Soon at a Theater Near You” to “Sneak Previews” to “Siskel & Ebert at the Movies,” the pair became more famous than many of the actors whose films they reviewed.

By 1986, the show reached more than 10 million people. The pair’s opinions could determine the fate of a movie, lifting some to box office success — the 1994 basketball documentary “Hoop Dreams,” for example, a low-budget effort that Mr. Ebert counted among the finest films in history — and dooming others.

“Siskel and Ebert go, ‘Horrible picture,’ and I’m telling you, [they] can definitely kill a movie,” actor Eddie Murphy said in 1987.

They rendered their film verdicts in thumbs: two thumbs up, an endorsement that studios splashed on movie posters in screaming fonts; two thumbs down, a universally dreaded condemnation.

“I liked it better before we had the thumbs,” Mr. Ebert told Playboy magazine. “Then, at least, you were allowed to have an opinion, like, ‘I enjoyed this movie,’ or ‘a hilarious film.’ I’d like to be able to give a sideways thumb occasionally.”

With his fame, Mr. Ebert launched a movie-reviewing franchise. He lectured widely, taught classes at the University of Chicago and wrote more than 15 books, including a novel, a cookbook and an annual anthology of reviews. In 2005, his name was added to the Hollywood Walk of Fame.

In 1999, he started Roger Ebert’s Overlooked Film Festival in Champaign, Ill., later renamed Ebertfest, to celebrate films that were either long-forgotten (the 1955 film adaptation of the musical “Oklahoma!”) or had never found the audience Mr. Ebert thought they deserved (“On the Ropes,” a 1999 Oscar-nominated documentary about three boxers).

But he considered himself a newspaperman at heart.

“The question from people that gets me the most is, ‘Where’s Gene?’ ” he told Editor & Publisher in 1987. “My answer is usually, ‘Who cares?’ Believe it or not, I was a movie critic before the TV show, and I’m still a movie critic.”

His reviews, which numbered in the hundreds each year, appeared in more than 200 newspapers across the country. The best movies, he said, challenged viewers’ understanding of the world and forced them to rethink their opinions. But all movies deserved to be judged according to their own ambitions, from French New Wave films to dusty Westerns, he said.

“If you try to apply the same yardstick to the new Godard and the new John Wayne,” he told Time magazine in 1970, “you’re probably missing the point of both films.”

Roger Joseph Ebert was born June 18, 1942, in Urbana, Ill. His father was an electrician, and his mother was a bookkeeper.

He was an only child, who stumbled early onto his two passions — movies and newspapers. As a boy, he spent Saturdays watching double features at Urbana’s Princess Theater on Main Street. And when a family friend took him on a tour of the newsroom at the News-Gazette in Champaign, he went home and began publishing a neighborhood newspaper out of his parents’ basement.

He served as the editor of his high school newspaper and by 15 was publishing a sci-fi magazine called Stymie and making 75 cents an hour covering high school sports for the News-Gazette. Two weeks before his father died in 1960, Mr. Ebert was awarded a prize for sportswriting from the Associated Press. It was an honor more important to him than the Pulitzer, he later said, because his father knew he had won it.

As a journalism student at the University of Illinois, Mr. Ebert edited the college newspaper and joined the Campus Film Society. He graduated in 1964 and went on to become a doctoral candidate in English at the University of Chicago. He never finished, choosing instead to accept a job at the Sun-Times as a feature writer in 1966.

The paper’s film critic retired the following year, and Mr. Ebert got the job.

He was 24 and didn’t know much about moviemaking, he later said. He learned by watching more than 500 films a year and by jumping into the industry, writing a screenplay for producer Russ Meyer, who had a legendary penchant for big-busted leading ladies.

Mr. Ebert had befriended Meyer after writing a letter to the editor of the Wall Street Journal. “His films are more alive and interesting than most current action pictures costing 20 times as much,” Mr. Ebert wrote in 1968. “And his heroines are technically interesting as well.”

They spent six weeks producing the 1970 film “Beyond the Valley of the Dolls” for 20th Century Fox, a rare venture by a major studio into X-rated filmmaking about the rise and fall of an all-woman rock band.

“As funny as a burning orphanage,” Variety said at the time.

“An indestructible cult classic,” Mr. Ebert countered 33 years later in the Sun-Times.

“Quite frankly and in all due modesty,” he wrote, “I think it is the best rock camp horror exploitation musical ever made.”

After contributing under pseudonyms to three more Meyer films, Mr. Ebert resolved not to dabble again in movie production.

“It’s a conflict of interest. When you’re a film critic, you have to stay away from that,” he told the Los Angeles Times in 1986.

Mr. Ebert lived as a bachelor until 1989, when he met Chaz Hammel-Smith (later shortened to Hammelsmith), a Chicago lawyer, through friends. They married on Mr. Ebert’s birthday in 1992. “There’s a British beer that has an ad I used to look at in the subway in London,” he said later. “It said, ‘Refreshes the parts that others do not reach.’ And that was Chaz.”

She survives, along with a stepdaughter and two grandchildren, according to the Sun-Times.

When Siskel died in 1999 from a brain tumor, Mr. Ebert continued hosting the weekly TV show — first with guests, then with fellow Sun-Times writer Richard Roeper. Mr. Ebert left the show in 2006, when he lost his voice after surgery to remove part of his jaw, where cancer had surfaced for the third time since 2002.

He continued to make public appearances when his health allowed. In February 2010, a striking portrait of Mr. Ebert with sections of his jaw missing appeared on the cover of Esquire magazine.

“I was told photos of me in this condition would attract the gossip papers,” he wrote. “So what? I have been very sick, am getting better and this is how it looks. We spend too much time hiding illness.”

Mr. Ebert communicated in his last years through his wife; with the aid of a computerized voice; and by writing in a notebook or on a slate he carried with him. He also spoke on the Internet, where in 2008 he began keeping a personal blog, opining on matters political, personal and professional.

He published his autobiography, “Life Itself,” to a sparkling reception in 2011.

A good critic “doesn’t have the answers, but he can be an example of the process of finding your own answers,” Mr. Ebert wrote on his blog in 2008.

And if his movie-reviewing shows had any lasting utility, he wrote, “it was in exposing viewers, many of them still children, to the notion that it was permitted to have opinions, and expected that you should explain them.”