DuracellEnergizer said:

Now that I think about it, it would be kind of interesting if Ep. VI had ended on the same note as Dune, with Luke becoming the new Emperor - and eventually a reluctant dictator - ala Paul Atreides.

It certainly would have paved the way for an interesting sequel trilogy, at any rate.

Are you referring to the bits in Making of ROTJ where Kasdan suggests exactly this ending? I think it's a very interesting potential story direction as well.

Of course it would have echoed not just Dune, but also the much older John Carter of Mars series, whose first trilogy ends with John Carter becoming Warlord of all Barsoom. (Along with the ending of The Hidden Fortress, this is probably what Lucas intended to parallel with the "coronation" scene at the end of the original ANH rough draft.)

But as Edgar Rice Burroughs was much more idealistic than Frank Herbert, John Carter is a much more benevolent ruler than Paul Atreides. For one thing, he doesn't unleash a galaxy-wide holy war that spills oceans of blood.

Alex Raymond's Flash Gordon, on the other hand, was offered the rule of Mongo after the downfall of Ming the Merciless, but refused--he stepped aside to let the rightful heir Prince Barin take over (not as King, mind you, but as a President) and hopped the first rocket back to Earth. It's Flash Gordon's altruistic refusal to take on political power that Lucas probably wanted to evoke in ROTJ, rather than Herbert's Atreides Empire with its inevitable decay into despotism.

Incidentally, Mongo after Ming seems to be a federation of constitutional monarchies--it's referred to as the "United Republics of Mongo" and the overall head of state is a President, but the individual realms of the planet retain their royal sovereigns. This is probably more or less what Lucas imagined the Republic as being like (applied to a galactic scale) when he wrote ANH.