My Three Favourite Film Critics (in no particular order):

Roger Ebert- I like Ebert for two reasons: he knows and loves movies, and he's an entertaining writer. Surprising for a critic of his fame, Ebert also seems to lack snooty pretensions and is able to enjoy Hollywood blockbusters as much as Iranian character studies (provided he's in the right mood).
Sample Reviews: Good & Bad

James Berardinelli- Berardinelli may not have Ebert's way with words, but his taste is impeccable and his reviews are quite intelligent. His thoughts are well argued and I usually find myself agreeing with him.
Sample Reviews: Good & Bad

Steven D. Greydanus- Greydanus, a Catholic, is a critic I began to read after stumbling across his thoughts on Bergman's The Seventh Seal at rottentomatoes.com. He's the finest Chrsitain critic I've read (others I've come across simply look for sex/profanity/violence and condemn it all without a second thought). He grades movies on two axes- moral/spiritual value as well as artistic value- and recommends only those films which score highly in both areas. (Since you're probably wondering, Steven Greydanus is no relative of Rich Greydanus.)
Sample Reviews: Good & Bad