Return of the Jedi is not the worst film of the original trilogy.
What is in your opinion?
The otherwise obvious choice, A New Hope. But only barely. I love 'em all, but I think A New Hope is the weak link. I do understand most people’s criticisms of Return of the Jedi, but the perceived flaws of the film are things that do not bother me at all, or at least not anymore. Ewoks, for example, are one aspect I’ve come around on.
A New Hope introduces many of defining characteristics of the franchise, i.e. a rebellion fighting a war against a tyrannical empire, space-wizard samurai, cocky smugglers with questionable morals yet hidden hearts of gold, ruthless bounty hunters and a seedy criminal underworld, space battles against impossibly constructed space stations of mass destruction, crawling around on or in areas of space stations not meant for crawling around in order to evade hostile forces, etc. Most of these aspects are expanded upon and fleshed out in the next two films to dramatic and/or universe-build effect. Empire Strikes Back and Return of the Jedi is where Star Wars fully captured it’s tone and identity and they will always be the 1st 2 things that pop into my mind wherever Star Wars is mentioned. Granted, The tone of RotJ is less consistent than the others, but it still has many classic scenes (many of my favorite scenes series-wide) that have defined Star Wars and influenced many stories going forward, both inside and outside the franchise, to good and bad effect.
Again, it doesn’t really matter that 4 is my least favorite, as I love 'em all. Between 4 and 5, my least and most favorites of the trilogy, there’s really only a 1 point difference on the 10 out 10 scale. I just think 5 and 6 is when Star Wars truly became Star Wars whereas 4 was the blueprint provider.