That could be debated.
I still think "Empire Strikes Back" is a perfect film. And, I'm sure there are other examples...like maybe "Raiders of the Lost Ark."
I agree original ESB was pretty much the perfect film, it loses perfect status with the special edition because of changing Boba Fett's voice and chopping up the scene of the Falcon escaping bespin just so we could see how Vader arrived at the Executor, as if we couldn't reason it out for ourselves and dropping a great vader line "Bring my shuttle" in the process. Apparently George Lucas thought it was pretty good too because it was the one he tried to screw up the least with changes.
Not too mention, breaking the tension after the Luke/Vader fight when Luke falls (seemingly) to his death with the Emperor's scream taken from ROTJ.
Now, I didn't mind the additions to Cloud City (e.g. Creating windows to show the vastness, and extending the initial Millennium Falcon landing) but, yeah, ESB didn't really need any tinkering.
I love TESB, it's my favorite Star Wars films and one of my all-time personal favorite films...but it loses points in the "perfect film" category because it's very much the middle chapter in a trilogy. It wouldn't have worked nearly as well if it had been a standalone film. It benefits both from the characters and setting having already been established in a very popular first film, and from being able to end on what would have been a very awkward and unsatisfying note for a lone movie.
Raiders, OTOH...that's the perfect film in my book.
True...true. I guess as a sequel it's perfect....because so many sequels fail. Even "Captain America: Winter Soldier" - as good as it was - managed to be
huge improvement over the first film, but CinemaSins on Youtube did a good job in pointing out the many flaws of the film.
Interestingly, CinemaSins has yet to do ESB or even "Raiders"...