For me it was between 4 and 6.

The first 3 episodes which was filmed in recent years definitely wins in terms of aesthetics and CGI, yet the storyline was rather rushed and awkward. The first episode was relatively enjoyable, but I felt that the 2nd and 3rd episodes were rushed through far too quick, as if a lot of parts were cut off in the editing process. And the overusage of CGI in the 2nd (the robot factory part and the final clone trooper battles) and the 3rd (Obiwan and Anakin's duel in the lava pit) were too much to be palatable. It was as if I'm watching a video game more than a movie.

Back to the older episodes.

4th was the beginning of the Star Wars movie phenomenon, and despite its relatively cartoonish special effects in today's age, it was a revolution back in the old days.

5th had a very dark theme as the empire totally crushed the rebels, but somehow I didn't like the fact that the ending was abrupt and left hanging. Yes, it was a deliberate gimmick to prepare viewers for the final episode, but it just wasn't exactly my cup of tea. That's not to say I didn't enjoy it though.

I picked 6th episode as my favourite because it had better looking CGIs compared to the 4th episode, and most importantly it showed the character development and maturation of Luke Skywalker, as he grew from a naive kid into a noble hero who not only saved his people, but most importantly released his father from eternal damnation. The final part where the Sith Lord tried to corrupt Luke was well done, as viewers could feel how sadistic the Sith Lord could be; while at the same time feel the inner struggle of Luke as he fought to resist the temptation of the dark side.

And of course I liked the symbolisation of an entire new dawn to civilisation as the empire was brought down. Old characters (Anakin, Sith Lord, Yoda) who played a role in the dark past either died or was defeated, leaving the new generation to build a better tomorrow.

My only complaints about the 6th episode was the weird inclusion of the Ewoks.... They were there just to add some comedy

Results of the poll are not important, the main thing is that people who voted post their opinions about all the episodes so we can know the pros and cons of each movie.

Seems like almost everyone hates the Ewoks