GL didn't create much of the OT by himself. I remember reading that Vader's full body suit concept was created by one of his artists based on an early draft that had Vader space-walking to another ship. What he did was to create a rough plot line, assign roles and gather ideas, even the ANH screenplay wasn't written only by him. But he sure is one hell of a producer, probably one of the best around, and he sure knows how to make money from movies...