Here’s my ranking of the films (videos in the case of Eps 2 & 3) on a scale of inventive to safe:
On the Inventive Side:
1: Star Wars - A giant personal risk by Lucas, and an unparalleled combination of genres that launched a franchise.
2: The Phantom Menace - Jar Jar and a Leave It To Beaver Anakin Skywalker make this an arguably suicidal gamble for Lucas, in terms of credibility. Regardless of its success, it was remarkable.
3: Empire Strikes Back - A radical departure from the plot structure, tone, and focus of the first film that succeeds in being at least as good as the original.
4: Attack of the Clones - After the divisiveness of TPM, Lucas had every reason to retreat into what worked for the Original Trilogy, yet he made the first major motion picture to be shot entirely digitally. Also making a digital Yoda. That is some major chutzpah.
5: Rogue One - The first Star Wars film without a lightsaber duel, one that focuses almost entirely on normal people in the Star Wars universe. A war movie in a fantasy franchise is gutsy and breaks new ground.
On the Safe Side:
6: Return of the Jedi - The film that has been called on these forums the ‘contractual obligation album’, it is an attempt to end the saga in one movie rather than the planned 4. Another Death Star, a return to Tatooine and Dagobah, and filming in the redwood forest for bugetary reasons.
7: Revenge of the Sith - A continuation of the poor cinematic choices of AOTC, Revenge brings almost nothing new to the table, and ends in one of the most overly explanatory ways possible.
8: The Force Awakens - Our heroes crash land on Not-Tatooine, escape in the Millennium Falcon to Not-Dagobah, the Not-Empire fires a Not-Death Star at Not-Alderaan, then Han, Leia, Chewie, and C-3PO all go to Not-Yavin 4 to plan an attack against the Not-Death Star and Not-Luke fights Not-Vader.
This is only one metric for determining the quality of the films, but I think this is one of the main reasons that the 3rd film in a trilogy hardly ever reaches the level of the first.