Undoubtedly the most famous and one of the most productive film reviewers in history, Roger Ebert, who died Thursday at the age of 70, was better-known than many of the stars he wrote about. For 35 years, he was involved in the production of a television show, that at its peak was syndicated to more than 200 stations and made him a rich man. He won a Pulitzer Prize, maintained an award-winning website, and, when his voice was silenced by cancer, became a force in the Twitterverse, engaging in feuds with everyone from Sarah Palin supporters to Jackass fans.

Though better known and more ubiquitious than such contemporaries as Pauline Kael and Andrew Sarris, Ebert never claimed their intellectual cachet. His own reviews were cleanly written, populist and personal. I once asked him in an interview if he had any interest in film theory and he said that he didn't, because he was interested in movies as "experience," not as "phenomena."

Ebert was certainly aware that younger writers and cinephiles mocked the thumbs-up/thumbs-down ranking system, treating it as a dumbing down of serious criticism. The idea, he said, was that the television show would encourage film fans to look to his other work, where he offered more analysis and detail. As for his notorious critical generosity – he gave a lot of four-star reviews – his justification was simply that he really liked a lot of movies.

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Yet over the past couple of decades, as mainstream movies became more wrapped up in sequels, comic books and cartoons, Ebert began to look less like the everyman critic he had once seemed, and more like a highbrow standard-bearer. Week in and out, he probably did more to expose international cinema, U.S. independent film and documentaries than anyone else in the media.

He was also a champion of editorial, rather than advertising values, dismissing clams that reviewers have too much power: "Whenever I'm asked if critics have too much power, I say the same thing," he told me in an interview. "I don't have enough power. A studio with a $20-million advertising budget that can have teenagers across the country lined up at 6 o'clock on a Friday night to see a movie has real power. I'd like to write a review a really good film that boosted its box office by 50 per cent some time but there's no evidence that this ever happens."

For anyone interested in films and film criticism, it was impossible not to be struck by his impact, both in a slightly negative sense – creating a cartoonish image of the testy movie judge – but also as a champion of film in its wide variety of forms. .

One example of how that passion made a difference was his early championship of the Toronto International Film Festival through his friendship with one of the festival founders, the late Dusty Cohl, who he first knew as a drinking buddy (Ebert gave up alcohol in 1979).

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In recent years, Ebert wrote so much about himself, his childhood and his health ups-and-downs, it seemed he was talking more rather than less. I had the sense that the disease was an inconvenience but not a tragedy because he still had his writing voice, which ultimately mattered much more than the public profile.

In early December, when he wrote that he had a "slight and nearly invisible hairline fracture on my left femur" it seemed insignificant.

Then, a few days ago, he wrote that the fracture was because of cancer and that he would be undergoing a "leave of presence," to undergo radiation and cut back on his work. He presented it as a positive thing, a chance to take the time to review only those movies he really cared about for a change. Today, it feels hard to grasp that that there won't be a further tweet or blog update on his current leave.