Alfred Hitchcock, Quentin Tarantino, Peter Jackson... all directors renowned for their ability to put themselves into their movies - an act which is absolutely not distracting and definitely doesn't kill the immersion inherent to watching a motion picture at all. George Lucas, on the other hand, usually steers well clear of the camera - if he's making a cameo, he's making it in other people's flicks, and if he absolutely has to get involved in his own pictures, he's offering up some handy voice work (when he had a nasty cough, Lucas recorded some of the sounds later used for General Grievous). Then again, there is that bit in Revenge Of The Sith where he turns up with his real-life son dressed as a fat blue alien man named Notluwiski Papanoida, who is - according to the Star Wars canon - a playwright. Not a good look for you, George. Not a good look.
Sam Hill is an ardent cinephile and has been writing about film professionally since 2008. He harbours a particular fondness for western and sci-fi movies.