When I rank the seven films I have to include episode 4 twice, because there are two almost distinct films there, and the additions that Lucas made change it enough to impact its quality as a film. I’m talking the 1997 major changes…not the other minor incremental changes that have happened at least two more times. Also, the 1997 changes to Jedi and Empire are minor enough to not change their ranking (for me, anyway — those who dislike the new ending to Jedi may disagree, but part my problem is I don’t think Jedi is nearly as good as other people think it is).
As noted in this article — there is a tremendous gap between Attack of the Clones and any other episode.
6. Jedi (and these could be 6a/6b for all I care)
5. Episode 4–1997
2. Episode 4–1977