Do you think it would have been more gruesome or dark?
I expect a different arch for Vader, as if he planned his revenge on his master using Luke's help.
Could have been interesting.
But Return is more in line with the prequels (if that matters).
"Revenge of the Jedi" was just a title, it wasn't a different movie. They were already well into filming when they made the title change.
shareYeah, like movies do not radically change in tone or story well into filming...
shareSure, but the production history of this movie's been documented pretty well so we pretty much know for sure there weren't any major changes during filming.
In fact there arguably weren't any truly radical changes at any point in the production - some of the early script drafts had differences in settings and characters (the Emperor's throne was at a city planet (this would've been what Endor was a moon of), Admiral Jerjerrod was more openly antagonistic with Darth Vader, there were two Death Stars under construction, etc.). But the story beats and overall tone were pretty consistent all throughout. There was always Jabba the Hutt on Tatooine, there were always Ewoks (it's true they were derived from a forest planet of Wookies, but that was during the drafts for the original Star Wars, not Return of the Jedi), and Darth Vader always sacrificed himself saving Luke from the Emperor.
The title was changed because there was some discussion within the production that it didn't really fit, and after the first trailer was revealed some fan reaction echoed that sentiment. They then ran a survey which revealed more people preferred "Return" over "Revenge" in the title, so they went ahead and made the change. It didn't accompany any change in direction for the film.
The title change came late into production. Posters were even made and some marketing was done with the Revenge title. Lucas didn't think that Revenge was a proper motive for a Jedi, I believe.
There wasn't a change in a direction for the movie, though. It's not like Luke was originally going to go on a rampage, killing every stormtrooper he came across even after the Empire fell.