An argument can be made about Charlie Chaplin's skill as a director as never directed anyone but himself in his films. There were other people in them, too, and whole scenes when he wasn't around, but they were ultimately all about him. But that's okay because there was a lot of Chaplin to go around.
Writer, director, editor and composer, Chaplin was the singular author of his films in a way modern directors can only dream of. They've gotten too large, too complex, to time consuming. It's hard to imagine a time when a short could be completed in a week. But in Chaplin's time, a card reading A Film By Charlie Chaplin really meant it.
The question is, would Chaplin have been Chaplin if he hadn't been in control of every aspect of production? Certainly he worked for other directors first, coming up as one of Mack Sennet's company players.
But it wasn't until Chaplin took over behind the camera, and switched to features, that the Chaplin we know -- the Chaplin of the Little Tramp, of "Modern Times" "The Gold Rush" and most importantly "City Lights" -- was born.
The telling sign, though, isn't Chaplin himself but the actors around him. Chaplin new emotion, new how to evoke it without sentimentality or mawkishness. More than that, he knew how to make his actors evoke it as well. Without Virginia Cherrill's heartfelt performance, "City Lights" would not be what it is.
A specialist of the Silent Era, Chaplin never stopped making them, even when he was making 'talkies.' The coming of the sound era didn't stop him, he kept working for many years after "The Jazz Singer" premiered making some of his best films in the sound era, but his output and his reputation are indelibly linked to that period. Which is probably what makes his films stand out so much. Silent films are in many ways the exercises in pure cinema, by necessity telling their stories entirely through visuals, acting through facial performance. A lot of the techniques of that period have been lost, but many remain and through them the great masters of the silent era still make their presence felt. And Chaplin was an unquestioned master of the silent film, perhaps the master. Because while the other greats of the time did their work with clever visuals and new techniques, Chaplin his style for the performances themselves.