For many of a certain generation, the phenomenon of incredibly disappointing third films in a trilogy began on May 25, 1983, with the release of "Star Wars: Return of the Jedi." The conclusion of what was arguably the most epic trilogy of all time was upon us and it was ... lackluster. Another Death Star? Lando piloting the Millennium Falcon? Teddy bears besting the literal universe-conquering Galactic Empire? After an inventive opening "let's get the band back together" sequence on Tattooine (the reveal of Jabba the Hutt was definitely worth the wait), the movie sagged when it should have soared. And it established the paradigm that the third film in a beloved trilogy will, ultimately, disappoint.

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!"

And even when a trilogy does end on a high note, as it did recently with "War for the Planet of the Apes," you can't help but brace yourself. There have been plenty of trilogies ("Pirates of the Caribbean," "Die Hard," and Indiana Jones come to mind) that have been watered down by the studio needlessly continuing the franchise or by an eagerness to instantly reboot the property. In other words, you can't even enjoy a good third film because you're just waiting for the bottom to fall out.But why are the third films in a trilogy such a letdown?

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.")

Then, there are of course, more practical things to consider. By the third film in a series, it's a certifiable franchise. That means that certain boxes need to be checked, products need to be more organically integrated, marginalized stars in previous films want a more substantial role, and the like. (It becomes even harder to get the A-level talent to come back for the third movie, especially after the first two are a hit. Just think about the epic wrangling it took to end the "Men in Black" trilogy and how we still don't have a third "Bad Boys.") There's also the desire to differentiate the film from those that came before it; sometimes those swings can be too broad and will leave the audience wondering what happened to the vibe they had earlier. You don't go to McDonald's and order a pasta salad and you probably shouldn't show up to a "Back to the Future" movie expecting a full-on Western.Other factors, especially if the second two films are shot together (usually a time-saving measure that places a more condensed burden on talent), are a proper allocation of time/resources and the fact that most of the time when they embark on those two-movie shoots, they have no idea how, exactly, the first sequel will play out, much less the third film. There was a protracted break in between "Pirates" movies because they actually had to release the second movie; production didn't resume until that film had been released. Filming together also means that there isn't any room for course correction. The Wachowskis were well on their way to a conclusion that was equal parts eastern philosophy and Japanese anime and the lukewarm reaction to "The Matrix Reloaded" wasn't going to make them deviate.

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.