Roger Ebert wasn't that well known outside the US, but he was perhaps the only film critic that many Americans would be able to name, and did a show with Bob Siskel that made reviewing less academic and more personal. He had no credentials however: he started off in journalism, happened to be handed the movie review column to cover at the Chicago Times, and flew with it. He did get slack for just just going on things whether he liked them or not regardless of genre (he might give a glowing review to a popcorn film, or a damning one to an intellectual one and vice versa). Still, you got a feeling for what he liked.
He wasn't as controversial as Sweetman ever was, but he was adamant in whether *he* liked it. And he did get slack for not lowering the standards of reviews!
While I do wish someone would rein Sweetman in a little in terms of his disparaging remarks (yes, the 'Linda' comment was too far), he is fairly consistent in what he likes regardless of popularity, which I give him props for.