A character who rules over a multi-billion-dollar global movie franchise always deserves a grand entrance. But “Pirates of the Caribbean: Dead Men Tell No Tales” and “Alien: Covenant” raise the question: How grand can your entrance really be when you’ve never gone away? In “Dead Men Tell No Tales,” Jack Sparrow, the sloshed freebooter who’s like Captain Morgan on opioids (hasn’t he heard that they don’t mix?), first shows up as a dissipated mess, rousing himself to consciousness as he lies inside a great big metal bank overflowing with gold coins. For a moment, you think you’re seeing Johnny Depp wake up in his bedroom. But even as the series winks at the idea that Jack has seen better days, it leaves us with a non-winking reality: He sure has.

In “Alien: Covenant,” the Alien’s first appearance gives you a similar what’s-old-is-new-but-not-really feeling. We’re on a leafy planet, in rugged terrain that looks perfect for a camping trip; the novelty is that the Alien is going to explode into view not on a sterile spaceship, or inside a slimy obsidian cave with walls like a T. rex’s rib cage, but in the great outdoors. We’ve already seen microbes float into a crew member’s ear like pollen, which leaves you wondering what happened to the facehugger (as it happens, the facehugger is still around, which makes the film seem like it’s playing by two sets of rules, which it is, but never mind). Then the moment of truth arrives. There is much coughing and writhing, there is blood-vomiting, there’s a mood that strains to come off like shock and awe. But when the alien fetus bursts out, the audience feels a bit like an obstetrician presiding over his 10,000th birth. Yep, that’s what it looks like. Next!

It’s worth noting that in the original franchise era, the 1980s, when the word “franchise” was an inside-baseball syllogism that was only just starting to be used by people like Michael Ovitz and Jeffrey Katzenberg, almost all Hollywood sequels were bad — “Halloween II,” “Jaws 3-D,” “Poltergeist II: The Other Side,” “Amityville II: The Possession,” “Grease 2,” “The Sting II,” “Conan the Destroyer,” “Staying Alive,” “The Jewel of the Nile,” “Meatballs Part II,” “The Karate Kid Part II,” “Revenge of the Nerds II,” “Beverly Hills Cop II,” “‘Crocodile’ Dundee II,” “Ghostbusters II,” “Arthur 2: On the Rocks,” “Fletch Lives,” “Big Top Pee-wee,” “Caddyshack II,” “The Gods Must be Crazy II,” “The Fly II,” “Back to the Future Part II,” and on and on. There was a cynicism, not just among film critics but among the audiences who went to see these movies, that a sequel might turn out to be cheesy fun, but that it was almost always going to be an inherently second-rate bill of goods, because it was based, transparently, on commerce: taking the original movie and squeezing its appeal dry. The very word “sequel” had a déclassé aura.

That era, of course, is long gone. Franchises are the basic commercial architecture on which the movie business now rests, so the whole culture — audiences, critics, the industry — has a vested interest in viewing this situation without cynicism. Besides, in our era, there have been enough artful and transporting sequels, from “The Dark Knight” to the “Bourne” Films to the “Before Sunrise” films to “Toy Story 3” to “Mad Max: Fury Road,” that one’s hope can always burn bright. Yet that doesn’t mean that the old rules don’t apply. One of the reasons the word “franchise” passed from industry talk to a colloquial term is that it sounds strong and powerful. You’re not just seeing a movie, you’re glimpsing a part of something larger. You’re not just watching it, you’re joining it. But it can be healthy to return to the mindset of the ’80s and remind yourself that a sequel is often just a sequel: a movie that has no organic reason for being, even if it pretends otherwise.

The “Pirates of the Caribbean” and “Alien” films have hung around as long as they have because of the promise that they’ll sustain the high of what they’ve done before. But that’s a none-too-grand illusion. In the case of the slovenly, nonsensical, tossed-together “Pirates” films, the promise now runs on fumes; in the case of the “Alien” films, the promise just grows more pretentious, as if the backstory of the Alien creature were part of some vast enthralling mythology that we’d all been craving to know. At times like this, it’s worth recalling the simple lesson of lousy ’80s sequels, which is that nothing kills a franchise like sheer repetition.

If you live by the pirate sword, you should be prepared to die by the pirate sword. There was always a built-in meta aspect to Johnny Depp’s performance as Jack Sparrow. In the original “Pirates” film, “The Curse of the Black Pearl,” in 2003, he wasn’t just a smart actor giving a stylized performance as a dissolute, self-centered rummy buccaneer who always managed to spit out a slurry line that was, in its chasing-logic-around-a-bender way, more literate than you expected. He was an actor of hip idiosyncrasy who went his own way. So when he agreed to be the hood ornament on a Disney movie franchise based on a Disney theme-park franchise, there was a cosmic irony to the casting. Depp, through his conviction and charisma, turned what should have been the ultimate act of slumming into a way to have his gold and eat it, too. He was the tongue-in-cheek soul of the new family-friendly machine.

His performance, however, began to look like good old slumming around the time of the third “Pirates” film, “At World’s End” (2007). For a while, Jack Sparrow was just another thing that he did; then it became the main thing that he did. And that changed the way the character came across. The whole power dynamic got flipped. Instead of being an actor who lent a square franchise a touch of cool, all because he was staying loose and having fun with it, Depp became publicly chained to what the franchise represented, since it was now the key factor holding up his brand. Depp’s whole off-camera look — the rings, the tattoos, the leather bracelets, the multiple earrings, the necklaces, the facial hair, the whole endless adornment of it — first presented itself as a series of fashion signifiers connoting his rebel independence. But then it began to play like he was becoming Jack Sparrow of Beverly Hills. And the tabloids (the toxic divorce, the money woes) only added to that. It was one thing for Jack Sparrow to be a dissolute troubleshooter chasing the gold; it was quite another for Johnny Depp to be.

Is it any wonder that the character has no lightness left, and nothing left to surprise us with? In “Dead Men Tell No Tales,” Depp delivers one line that, to me, has some of the sparkle of old. The movie’s hero, played by Brenton Thwaites, this week’s Aussie-pretty-boy-who-would-be-a-star, confronts Jack with the fact that he has no ship, no crew, and no pants. “A great pirate does not require such intricacies,” says Jack, and Depp tosses off the word “intricacies” with a myopic spontaneity that made me smile. The rest of the time, it’s dispiriting to see him go through the motions of a character who has run out of wit and juice. There is nothing left to discover, or enjoy anew, about Jack Sparrow. He’s like a sitcom mascot who has done everything but jump the shark.

Truly, though, he doesn’t look any more pickled than the Alien. “Alien: Covenant” is the sixth “Alien” feature, and what was clear 20 years ago, by the time of “Alien: Resurrection” (1997), is that you can take all the elements of this series — nightmare décor out of the H.R. Giger wallpaper collection; squishy hyper-sexualized imagery of birth and death; exoskeletal monsters with dripping silver jaws — and you can bang them together into a new shape, but the thing that can’t be recaptured, even by director Ridley Scott, is the essence of the original 1979 “Alien”: the sense of revelation, of seeing a monster that immerses the audience in transcendent horror.

In “Alien: Covenant,” the chest-bursting scene gets repeated so many times that after a while, I began to think: If the Alien is really such an advanced creature, why is it even bothering with all that gestation-and-delivery stuff? It seems, for the Jaws of Space, like such an inefficient way of coming into being. What’s inescapable is that a monster that’s supposed to chill us to our souls has become, after far too many films, as familiar as an old friend. And each time you make another “Alien” movie, you now only add to that feeling. More becomes less. Fear becomes reassurance. And something old can no longer be made to look like something new.