I don't think I would think of Lucas as such a terrible writer if he didn't refer to himself as a "genius, mastermind, and innovator."
Like I recently read about Hal Sparks (a comedian) saying:
"I've never bought that George Lucas had the whole story arc planned out from the beginning; especially when you look at the original Star Wars poster and see Princess Leia is clinging to Luke's leg. You'd think if George thought this through all the way to Jedi he would have brought that up in the marketing meeting, and say something like, 'You know that's his sister, right?' They probably would have had to take some of the kissing out too."
-kv