I rank these films thusly: The Empire Strikes Back, A New Hope, Revenge of the Sith, Return of the Jedi, The Force Awakens, Attack of the Clones, and The Phantom Menace.
Sith opens with an awesome space battle. It's not followed very long as the point is following Obi-Wan and Anakin in a rescue of the kidnapped chancellor, but while that battle was on screen it was fantastic. Lots of stuff happening in every frame. Jedi, however, spends a good bit of on screen time on its big battle, and I will give it the edge for a different reason altogether - it was accomplished entirely with models and blue screen, no CGI, completely old school visual effects.
I rank Sith ahead of Jedi because of the freaking Ewoks. To me that was the preview of the things that a lot of people here gripe about the prequels. George Lucas re-invented the teddy bear. I hated every moment with those f-ers; they were clearly a marketing device to sell stuffed animals and other toys. I do recognize the role they played in the movie, but as with Jar Jar Binks, I accept them for what they were and enjoy the overall movie without allowing their presence to ruin the entire movie for me. I will say that Jedi would have been better had they had Wookies rather than teddy bears.