Ebert is the man. He is a great, solid writer, and not just about films. I'm amazed how often I agree with him 100% about social and political matters, and I'm always impressed at how well he analyzes things and then explains them without excess.
I think I probably disagree significantly with his opinion of a film about half the time. That's a lot. But I still always want to read his reviews. Sometimes I'll see an older movie and like it and be pretty sure he didn't like it, and I'll go hunt down his review because I want to know what he said and why.
And, although this is admittedly as egocentric as it sounds, when I agree with him, I don't think, Wow, this guy is really smart! Instead, I feel like my own opinion has been somewhat validated. I usually don't feel that way about other people's opinions.
Incidentally, that sitcom of his and Siskel's may never have materialized, but they did a brilliant episode of The Critic, with Jon Lovitz, where they have that love-hate relationship. They split up, and both of them audition the title character as a replacement partner . . . and try to turn him into the other member of their duo. There's also a priceless scene of the two of them as kids, reviewing films from a lemonade-stand sort of setup. At the end, they're brought back together by their mutual so-so review of Sleepless in Seattle, which they regard as an unnecessary remake of An Affair to Remember, which they agree wasn't THAT great in the first place.