To call someone a Roger Ebert is to say that they are a naive pompous asshat with no credibility. It is most often used to describe people who
spout their opinion on subjects they know little to nothing about.
This slang term became increasingly popular when the
Pulitzer prize winning
film critic declared that "video games can never be art," all while stubbornly refusing to play any of the great games of the medium. He found it unnecessary to experience an art form before denouncing its entire artistic merit.