There have been many examples of this phenomenon in the years since; each carrying with it unique baggage and problems. But one thing is certain: if the first film intrigued you and the second film blew you away, then the third film would be the movie-going equivalent of warm lettuce. Oddly enough, the films best equipped with avoiding this trope seem to be the Marvel Studios films; think about how excellent "Iron Man 3" and "Captain America: Civil War" were, and how unbelievably good "Thor: Ragnarok" looks.

Obviously, opinion and box office will shift and sway, but there have been a number of films since "Return of the Jedi" that have been absolute duds: "The Godfather Part III," Sam Raimi's "Spider-Man 3," "Blade: Trinity," "Robocop 3," "The Dark Knight Rises," "Back to the Future III," "Beverly Hills Cop III," "X-Men: The Last Stand" ... The list goes on.

It's gotten to the point where, when director Matthew Vaughn has brought up a third entry in the "Kingsman" franchise while talking about his upcoming sequel "Kingsman: The Golden Circle," you kind of want to shake him and say, "Stop at two!"

There's the most obvious issue of unrealistic expectations. If the first film is good and the second film is great then the third film should reshape your very conception of reality or it's going to feel like a bummer. The best way to enjoy the third film in a trilogy is to sometimes, even when they're problematic, is to accept them for their differences, especially if they are wildly ambitious and risky. (I'll go to my grave defending "The Matrix Revolutions.")

So will these trilogy-enders be any less disappointing?

It's impossible to say, especially with the studios' shifting away from self-contained trilogies towards larger, more integrated "universes" that have multiple series intermingling. The idea of a trilogy itself might be something of an antiquated idea in the years ahead.

For the finale of a trilogy to really succeed, everyone involved, from the studio down to the creative principles, have to really want to give audiences something that they've never seen before, while also honoring what came before. It's a high-wire act to try and pull off, but if it is successfully accomplished, you provide the rarest gift of all: a film series that goes out on top while leaving audiences hungry for more.