Watching the largely successful new Planet of the Apes trilogy as a triple feature the other night made me wonder, "How many trilogies have there been where each film is good AND the trilogy as a whole is good?"
By which I mean that each individual film gets a positive review on its own merits, without depending largely on its connections to the other two. But also that all three films connect together enough to where the trilogy has its own overarching story that plays out successfully.
I realized that I could only really come up with four examples.
Lord of the Rings - obviously.
Planet of the Apes - I prefer the first film, but all three are good to great films, and Caesar's arc across the three feels like a giant biography of a historical person.
The Dark Knight - The second and third are more closely intertwined, but obviously the first sets up dominoes that fall in the others.
Pirates of the Caribbean - Opinions will vary, but I enjoyed the first three films to varying degrees, and found the conclusion of the third a really strong one that should've ended the story.
Notable omission: Star Wars. I just don't find RotJ to stand up as a good film on its own. It's almost wholly dependent on story beats from the first two films, and our love of those films. Without them, it's a film that dies on the vine after the escape from Jabba.