Roger Ebert, a Chicago movie critic whose weekly TV show with crosstown rival Gene Siskel made him one of the most widely recognized and influential voices in film, died Thursday at a rehabilitation facility in Chicago. He was 70.He battled cancer on and off since 2002, when he had surgery to remove a malignant tumor from his thyroid and salivary glands. He had announced on his blog Wednesday that he was undergoing radiation treatment after a recurrence of cancer. His longtime newspaper, the Chicago Sun-Times, reported his death.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 blockbuster, and in 1975 he became the first film critic to win a Pulitzer Prize. But it was through bickering about movies onscreen with Chicago Tribune film critic Siskel that Mr. Ebert revolutionized film criticism, pulling it off the newspaper 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.The two journalists, fierce competitors at their day jobs, were unlikely TV 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.But they 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 films with a passion that occasionally spilled over into personal insults."For Gene, speech is a second language," Mr. Ebert once said."Nancy, please bring Mr. Ebert a bookmark so he doesn't lose his chin again," Siskel said."We were very close and friendly," Mr. Ebert once said of his relationship with his fellow critic, who died in 1999. "Except when we were fighting."As the show grew from local public television to national commercial syndication, the pair became more famous than many of the actors whose films they reviewed.By 1986, the show reached more than 10 million people across the country. 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, and two thumbs down, a dreaded condemnation.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, an 1999 Oscar-nominated documentary about three boxers).