This may be heretical, but I really think there's only one thing the three sequel movies can be about (and I haven't read ANY of the EU novels in that time period, so I'm going at this blind, but I've heard that at least some of this has been broached in the EU):
The war is over, Leia is trying to restore the government of the Republic, Luke is trying to rebuild the Jedi Order, when they are blindsided by the newly restored Senate, who demand that Jedi be outlawed on the very sensible theory: No Jedi, no Sith.
Luke objects, the Senate threatens to lock him up (he's Darth Vader's son! of course they try to lock him up!!!) Leia throws a fit, but in the end Luke goes into hiding (I kinda like the idea of Leia sending Han along to help him survive, being an expert in that sort of thing - we really never got enough of Han and Luke interacting for my tastes).
Meanwhile, Leia sensibly tells nobody (who doesn't already know) about her parentage. However, I've always wondered what would happen to a Force sensitive person who simply ignored their abilities, and whether that would be asking for trouble, Luke and Han are out of the picture and Leia would have no idea what the "symptoms" are of darkside-ism, to look out for in herself.
Leia has survived a terrible war in which her whole planet was destroyed, only to find the ingrateful bastards whose freedom she fought for, a lot of whom were probably happy to profit from the Empire, are now turning against her blameless, heroic brother, and would turn against her if they knew the truth. She's highly prone to anger, bossiness and self-righteousness, and she's completely oblivious to the danger she's in. If there's a better formula for creating a Sith, I can't think of one.
That retains the core of
Star Wars, which is basically that the Skywalkers are the most frakked-up family in the galaxy and just can't stop squabbling among themselves.

I just can't envision
Star Wars without at least one Skywalker kicking up shit. If the Skywalker and Solo children can be brought in on the fun, we could keep it going indefinitely, although I'd be more inclined to just carry the story over three movies spanning only a few years, without any time for kids to enter the picture as adult or even adolescent characters.
See, I always thought the acting was as equally to blame for Ani's dooshyness as the writing. Even the infamous "sand" line would have come-off better in the hands of a more competent actor. People say how much better Christensen is in other stuff. I don't see it. I've seen several of his other films (including the Stephen Glass film) and he just never impressed me.
He was a good casting choice if you assume Anakin is supposed to be a loathsome punk, because the actor is very good at playing loathsome punks (anyway, I hope for his sake it's just acting

) but if Anakin had been written like he should have been, I think a different casting choice would have been required.
And it's true that no actor could have pulled off idiocy like the sand line, and the love-babble, etc. But maybe a better or at least savvier actor would have thrown the script in Lucas' face and called his agent.