The problem as I see it with the ending of Return of the Jedi is that it lacks emotional punch. This comes from the characters not being consistent with their motivations. For example, Luke has been taught to be "a Jedi." We are told over and over that a Jedi will not fight out of anger. Luke accepts this and even lets himself be captured by Vader with the hope of turning him to the good side. This is reminiscent of Ben Kenobi letting Vader kill him, a tremendously emotional moment.
But Lucas doesn't know how to write a dramatic ending without a fight, so he gives Luke a pretext to get angry and start fighting -- the discovery that Leah is a Jedi. That's both inconsistent with his Jedi training and it makes all of his motivations throughout the earlier part of the film irrelevant. Essentially, Luke's Jedi training is now pointless.
Vader also gets shortchanged. Vader was once good, but got co-opted. Luke thinks he can be saved and there is some hint of that, but Vader doesn't really struggle with it at all until the Emperor is on the verge of killing Luke. Then he suddenly saves Luke and thereby saves himself. Meh. Too easy, too obvious.
The Emperor too gets shortchanged. He has this influence over Vader, but he never gets to show it. There is no struggle for Vader's soul. He sucks at converting Luke too. And besides that, this most powerful of Sith Lords is basically chairbound.
The result of these defects is that the finale of the film, the climax of climaxes... is kinda dull. Want proof? Ask yourself if anyone talks about the lightsaber battle being all that special.
So think about this instead...
The scene begins aboard the Death Star. Luke has given himself up to convert Vader. It seems to have failed. The Emperor makes a sales pitch to Luke, but Luke holds firm. Luke, at the same time, keeps trying to convert Vader. Finally, the Emperor decides to switch to torture. When he does, Luke frees himself and escapes into the dark maze of the unfinished room.
The Emperor orders Vader to hunt Luke down and kill him. Vader, however, shows conflicting emotion and hesitates. His hesitation angers the Emperor. The Emperor takes his own lightsaber and goes after Luke, leaving Vader out of the chase.
As the Emperor hunts Luke, Luke is doing his best to re-awaken Anakin Skywalker inside Vader by talking about father-son relationships. It frustrates the Emperor that he needs to fight Luke for Vader's soul and he becomes increasingly angry. Meanwhile, Luke remains calm. He refuses to draw his lightsaber. He knows he cannot beat the Emperor in a fight because the Emperor is too good of a swordsman, plus he knows that if he draws his lightsaber, Vader will respond instinctively to the danger and will revert to the Dark Side. He also realizes that if he does fight, he will violate his Jedi beliefs and will corrupt himself. Hence, he is stuck with nonviolence.
Finally, the Emperor finds Luke and starts destroying the object blocking him from Luke. At this point, Vader finally loses control and blocks the Emperor's blow. The Emperor pushes him aside and says that he has taken everything else from Vader, he will now take his son. Vader goes into rage mode and brutally attacks the Emperor with his lightsaber. The Emperor is stunned by the force Vader uses because he combines both the Force and the Dark Side of the Force in his attack because he now has a foot in both camps. Vader overpowers the Emperor and knocks him to the ground with his blows. Then in one final strike, Vader hits the Emperor's lightsaber so hard that he cuts through the Emperor's lightsaber blade (a seeming impossibility) and kills the Emperor. However, using this much force mortally wounds Vader and he dies after a quick discussion with Luke about regret.
I think this would be much more true to the ideals of the characters. I think the battle for Vader's soul would be much more dramatic than the half-assed lightsaber fight between Vader and Luke. I think the symbolism of cutting the Emperor's lightsaber in half would be amazing and would become the most talked about moment in the entire series. It would also finish the same cirle of betrayal that the Emperor started when he got Vader to betray Ben.