The ANH:R version of Obi Wan/Vader dueling, at least to me, brought the duel a little closer to the PT. The shot of Vader blocking Obi Wan's saber in a close-up shot of Vader's head reminded me heavily of a similar shot in TPM when a close-up shot of Maul showed him blocking both Obi Wan's and Qui Gon's sabers. But the original version of the duel wasn't very good anyhow, since the choreography wasn't very well done, so the edit improves upon it a lot. The ESB duel doesn't need re-editing other than special effects (think: glowing burns added in to where the saber hits metal, etc.)

ROTJ has a decent duel, but I never really liked the duel after Luke screams "NEVER!" because it looks like Luke is barely even touching Vader's saber half the time, as he swings wildly like someone who has never been in a duel before, even though he fought Vader in the previous movie! The music in those moments is what truly saves the duel from looking terrible. Just watch it without music and it looks silly. The bad thing is, not much can be done to fix that.

Slightly off topic, but if Ady felt inclined to, I'm sure he can fix the problems you're referring to. If he can make the cup line up with the alien's mouth in cantina in ANH:R, then perhaps he can make the sabers more convincingly make contact. He managed to work wonders on the Vader/Obi Wan fight. Perhaps we have a similar overhaul in store for ROTJ :)