I rate Revenge of the Sith the lowest because thats where Star Wars really died for me. Saw it for my 15th birthday and it was really one of those "end of childhood moments". Watching something you loved as a child and realizing it's pretty shitty. The begining you have the most shitty attempts at humor with the droids. Awful tone shifts with the complete seriousness and death with the Jedi stuff combined again with droid humor. Characters like Anakin acting like the biggest idiots and being manipulated in an idiot plot that was so dumb I could'nt suspend my disbelief, which is something I can do very well. I am not a nitpicker. If a movie works on some levels and is entertaining enough I'll excuse a lot. But Episode 3 is just so shitty. The dialogue, the staging, and the action. Just so wooden and unexciting. I've never been so bored of a lightsaber fight as I have been with Episode 3.
All the prequels are bad but, 3 is the one that sticks out mostly because people seem to excuse it as being the "dark" and "serious one".
Rogue One's plotting and storytelling is pretty awful. It's such a disjointed and stitched together movie that it's a shame. It looks great though and it certainly had an interesting premise and set-up. I'll be an edgelord and say the tone is fine with me. It's not that serious and Star Wars could use some space western/dirty dozen type stories.
Solo was ok, which is really all I can say. Nothing awful about it, but nothing super amazing either.
TFA is fine. It's a fun movie. I don't care that yes it's a ANH again. I don't like the worldbuilding and stupid world status quo though.
Which also means TLJ is worse in that regard as the lame status quo is made even worse. Still I like the overall theme and Rey/Kylo stuff. The Rose and Fin and Rebel Fleet stuff is awful though. Wish Rose and Finn had a better subplot. I'd rate it higher and find it an interesting movie, but I really dislike the Rebel Fleet stuff.
So my ranking is:
Empire>New Hope=Returns>The Disney Stuff(It's all equally fine to me)>The Prequels.