A funny thing about Lucas' reasoning behind changing the name of Episode VI.
He said he chose "Return of the Jedi" over "Revenge of the Jedi" after realizing the Jedi didn't really have something to get revenge for.
Then he used that word for Episode III, "Revenge of the Sith".
But that movie (Episode III) is a laundry list of things for which the Jedi could get revenge --while (unless I missed it) it never really explains what "revenge" the Sith are seeking.
It seems a better case could be made for the titles to be reversed-- "Ep. 3: Return of the Sith" and "Ep. 6: Revenge of the Jedi".
While I think Lucas also feels revenge is not something a Jedi master should consider worthy of his attention, I sure wish he'd stuck with that original title.