We had a big "should it have been Revenge of the Jedi & Return of the Sith?" discussion a while back (I think it was the ESB/ROTJ wishlist thread).
Personally, if Luke can forcechoke guards and slice anyone who gets in his way with his lightsaber, I don't see why he wouldn't be able to take revenge. Anakin (no longer Vader) sure takes revenge on Palpatine.
There wasn't any revenging going on in episode 3 anyway. The Sith just returned "with a bang".
Many here thought the title change was to drastic though, so we just left it there.