Despite Lucas having a reputation for not being able to do dark movies, and only being interested in kiddie films, I think THX and Episode III are more in line with what Lucas actually prefer's to do, than the really light stuff like TPM. When Lucas goes dark, it's nearly ALWAYS good. Think of THX, think of ESB (which Lucas was heavily involved in, whatever his detratcors think) think the the Tatooine sequence of AOTC and the Vader/Emporer/Luke confrontation during ROTJ.
Lucas has often spoken about how Episode III will sit well in the 21st Century, because of it's depressing tone, and how it will be his personal favourite because of all the betrayal. All this leads me to the shocking conclussion that rather than being a happy go lucky multi millionare-George Lucas is actually a pesemistic manic depressive!
