I prefer to pretend that the prequels were never made as they are utter crap with the exception of Revenge Of The Sith which was passable. My favorite is Star Wars, before they called it A New Hope. After that comes The Empire Strikes Back. Return Of The Jedi was ok, but the Ewoks nearly ruined it for me.
I'd say A New Hope was the best one, followed by Revenge Of The Sith. Both of them were excellent achievements in an already great series.
But in this order from best to worst:
1. Star Wars A New Hope (10/10) 2. Star Wars Revenge Of The Sith (10/10) 3. Star Wars Return Of The Jedi (9/10) 4. Star Wars The Empire Strikes Back (8/10) 5. Star Wars Attack Of The Clones (7/10) 6. Star Wars The Phantom Menance (which mostly blew chunks)(4/10)
Why is everyone so in love with Return of the Jedi? With the exception of the last 15 minutes of Luke-Vader-Emperor interaction (which is great and obviously critical to resolve the story of the entire trilogy), the whole rest of the movie is quite ridiculous in tone, acting and storytelling IMHO. Even Hahn, one of the greatest movie characters of all-time, seems to have some sort of 'carbon-freeze hangover' throughout the movie. Gone is his macho attitude and instead we are left with him telling Leia 'I love you' like a real wimp in one of the cheesiest scenes in the Trilogy, completely emasculating his character. Thank goodness his character was resurrected in proper fashion with proper Hahn-like attitude for Episode 7.
I agree that Return of the Jedi is horrific except for the Luke-Vader-Emperor interaction at the end (which is critical for resolution of the entire trilogy). But trying to rank the last three movies on your list from best-to-worst is like asking 'what is your favorite way to suffer'? I agree with your first 3 on the list though, but if ties are allowed I would probably put Sith and Star Wars in the 2nd position (depending on the day and my mood).