Can't copyright an existing word, so, no.
Particularly since it's
Revenge of the Sith, not Return.
Trivia:
The Return of the King was originally titled
The War of the Ring. Tolkien thought
The Return of the King as a title gave away too much of the story.
Not as much as, say,
Frodo Finally Gives In To The Dark Side, but meh.
Trivia #2: Sith is also an existing word. It's an archaic form of "since."