I certainly don't think the visuals are the only part that truly matter, but I do think they are the most important part of a film. It all matters, but cinema is primarily visual. Even a dialogue heavy film like 12 Angry Men is thrillingly cinematic because of the way the angles are chosen, making it seem as though the walls are gradually closing in, etc. 12 Angry Men could be performed on stage, with the dialogue as crisp as ever, but the cinematic claustrophobia would be absent.