Great question and super discussion!
I can't really choose. When I first saw RotJ at age 8, I was devastated that the
one Ewok was killed. As much as I loved the movie, I thought that Lucas and his compatriots must have been sadists for killing off that cute, friendly (nameless) little teddy bear!
As an adult, it's rather astonishing to me that an intergalactic war could have the death of one Ewok as its main casualty. I think that
someone should have died, although I'm not sure if Han was the right choice. (I don't have any other suggestions, either, though.)
I do think that Luke should have fallen to the dark side of the Force completely, but possibly temporarily. Maybe Luke should have been the one to have a heroic sacrificial death, after he was turned back.
Besides, if Han dies, then that leaves the path open to a Luke-and-Leia romance, a concept which will forever be "ewwww" in my mind.
While Lucas may have had the wrong motivation for giving RotJ a happy ending, I think the movies play better that way. I wouldn't want a bittersweet ending where the Rebellion is in shambles.
The happy-dark-happy ending structure makes the trilogy feel like the movements in a piece of music (as Lucas has often described it himself). The prequels, by their nature, couldn't do that. III was always destined to have the darkest ending, which means it goes happy-happy-dark. It just doesn't feel right.
Star Wars is by its nature a fairy tale, and fairy tales
should end with "happily ever after."
I can still distinctly remember standing in the theater as the RotJ credits played, and not wanting to leave because of the euphoric feeling I had from the way the movie ended. I wouldn't want to do anything that would take that away from my 8-year-old self.
When I talk to kids and to casual fans, many of them say that RotJ is their favorite. I think that many of them respond to the unambigiously happy ending as well.
So . . . someone major should have died, possibly Luke, but the films should still have had an overall happy ending, IMHO.
Does that answer your question?