Quick, name the greatest film by each of the following directors: Alfred Hitchcock, Steven Spielberg, David Lean, Robert Altman, Roman Polanski, Kathryn Bigelow, Jonathan Demme. Answers will vary (mine would be: “Psycho,” “Saving Private Ryan,” “Lawrence of Arabia,” “Nashville,” “Chinatown,” “The Hurt Locker,” “The Silence of the Lambs”), but whatever your taste, odds are that the movies you chose were not written by the director in question. (On my list, none of them were.) There are, of course, countless great writer-directors — Ingmar Bergman, Preston Sturges, Quentin Tarantino, you name it. So it’s not as if it has to be...