When “X-Men” debuted on July 14, 2000, superhero movies were at their lowest ebb in years. Even though breakthroughs in visual effects made it increasingly possible to bring fantastical superpowers to life, the vapid camp excesses of 1997’s “Batman & Robin” had curdled the whole idea of costumed heroes saving the day into something that felt more than a little silly.

Twenty years later, the “X-Men” movie franchise is coming to a close with its 13th entry, “The New Mutants,” in a vastly different landscape, with the superhero movie the dominant force at the box office for nearly a decade. And yet despite helping to launch the genre to its current cultural primacy, the “X-Men” movies themselves never quite led that charge, reliably successful but not (until more recently) breakout global sensations.

Unlike the cohesive Marvel Cinematic Universe, the “X-Men” movies are impossibly convoluted, filled with time-travel reboots, narrative contradictions, and outright nonsense. They’re also unfortunately freighted now by their association with Bryan Singer, the disgraced filmmaker who directed the first, second, seventh, and ninth films in the franchise.

But when these movies are good, they are great fun, capturing the zippy energy of the comic books as their mutant human characters explore and exert a seemingly limitless set of superpowers, from controlling the weather to manipulating metal to healing their bodies even after being ripped apart. And when they’re at their very best, these movies have also expanded the boundaries of what is possible with a studio superhero film.

Now that the studio that made and released the “X-Men” films, 20th Century Fox, is a subsidiary of the Disney Entertainment Complex, at some point in this new decade, the X-Men characters will almost certainly begin to show up within the Marvel Cinematic Universe, rebooted and refreshed for a new generation of audiences. Before that happens, however, let’s look back at the best, and worst, of what this franchise had to offer.