The word “beloved” is almost never used to describe a critic, but, judging from the comments I’ve been reading about him, the late Roger Ebert seems to be the exception. I think this is because he managed to give the impression that he was basically a decent person, even when he was being waspish. He was willing to admit that he was not infallible (which is unusual for a critic), and he was courteous towards people who disagreed with him.
Pauline Kael and Andrew Sarris had far more influence among cineastes, but Ebert reached a much broader audience, because of his shrewd use of first television and then the Internet. When Ebert and Gene Siskel started their Sneak Previews TV show back in the 1970’s, there was much skepticism that people would want to watch a show that was basically two guys talking about movies. (Critics derided them as “the Fat Guy and the Bald Guy”.) Yet the show turned out to be hugely popular, and it was much imitated. Part of the attraction of the show was the sometimes tense relationship between Ebert and Siskel. (I have a suspicion that they may have deliberately played this up a bit. In that respect, it can be argued that Sneak Previews was the first “reality” TV show.) Their “thumbs up/thumbs down” gimmick irritated many of their fellow critics, but Ebert was in his own way an entertainer who knew how to get an audience’s interest.
Over the years, Ebert praised a lot of movies that I didn’t really think were that good, though in that respect he was no worse than most other critics. One thing I will say for Ebert is that he believed that it’s legitimate to criticize a film for moral reasons, which is something I completely agree with.