Like many people my age, I was first exposed to film criticism by the show Sneak Previews which started broadcasting on PBS in 1975. Roger Ebert and Gene Siskel reviewed films while sitting in a movie theater giving them thumbs-up or thumbs-down. Since then, thumbs up or down have become a cliche. This show and their later show, At the Movies, have had many incarnations and many imitations since. I probably owe these two guys great thanks in saving me from movies like Tron and introducing me to great American cinema. If not for them, I may not have seen Apocalypse Now as a kid in the theaters when it first came out.
For those who think people who are critics do so because they cannot create their respective art themselves might find this interesting. Ebert actually has some screen writing credits under his belt. The most notable is the screenplay to the Russ Meyer cult film, Beyond the Valley of the Dolls, which some might say is not quite so notable.
You may have noticed that you haven't seen Ebert on television lately. He has not passed away but he did have a bout of thyroid cancer. He has had part of his jaw removed and he can no longer talk, eat or drink. He still writes reviews.