I think there’s a minor problems with RotJ, but I don’t think that killing off Han would have helped. I imagine that could have found a way to make it heroic and memorable, but it wouldn’t have helped fix the biggest problem, which was the Ewoks.
I’d read somewhere that it was originally going to take place around the Wookie planet, but George Lucas opted for the Ewoks for merchandising. I’m not sure if it’s true, or just someone wishing it was true, but I think it would have helped a lot. I kind of get the added point of the small, cute, technologically inferior Ewoks beating the Empire seems like some kind of victory for the little guy, but all it really does is make the Empire and the Rebels look incompetent. I think if they’d faced off against a race much more on their terms, perhaps the Wookies (or some other race) were enslaved, or just hadn’t quite built up the will to fight back until the Rebels arrive.
And since it was brought up, I don’t think the prequels are as bad as most others think either. I think there’s a lot of nostalgia involved in comparing them to the originals and I do think that the fact that the originals were lightyears ahead of anything of the time, which combined with 20 years of fond memories, nothing could have done as well. Sure, Matrix and LotR came out about the same time, and while they were cultural phenomena, they didn’t revolutionize the industry the way the originals did. Moreso, imagine if the Matrix sequels hadn’t come out when they did, but came out now or even 5-10 years from now. They’d be hated even more.
I do feel that there was some very poor dialogue, poor acting, and poor directing, but I think the general story actually works pretty well. Other than that, I think most of the mistakes were made in Episode 1, and they just never fully recovered from (eg, midichlorians, Jar Jar, the kid playing Anakin was just awful, etc); although, I do think the complete lack of chemistry between Anakin and Padme did put a damper on it all too. I think a little bit of a rewrite of the first movie, some more work on the dialogue, and making the romance more believable probably would have made enough of a difference.