Over the past few years, the Avengers, together and separately, have spawned a number of good, very good or reasonably entertaining movies. But with “Avengers: Infinity War,” the Marvel Comics franchise arrives at the stage of decadence.

There’s just too much of it. A victim of its own success, the movie has just too many appealing characters to stuff into one story. It’s no longer one team of superheroes fighting a single villain, but several teams fighting the same villain throughout the known universe, over the course of 150 minutes of screen time.

Eventually, the movie arrives at the ridiculous point where the action is cutting between two battles in two separate locations, all the while keeping track of a critical surgical procedure in the enlightened nation of Wakanda. Meanwhile, what people like most about the series — the colorful personalities — gets short shrift.

Even then, the very best moments in “Avengers: Infinity War” are playful, involving minor clashes between the flashy characters. In an early scene, Tony Stark (Robert Downey Jr.) is cooing with his girlfriend, Pepper (Gwyneth Paltrow) on a city street, when Dr. Strange (Benedict Cumberbatch) arrives inside a circle of fire. “It’s not overselling it to say that the state of the universe is at stake,” he says. What briefly follows is the fun of watching the movie’s two most smug, self-satisfied people get on each other’s nerves.

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There’s also the kick of seeing Peter Quill (Chris Pratt from “Guardians of the Galaxy”) suddenly become insecure in the presence of Thor (Chris Hemsworth), who is roughly the same physical type, only bigger, stronger, tougher and more handsome.

But “Avengers: Infinity War” is not about funny lines or situations. These provide some relief, but the movie is mainly about the action, which involves yet another megalomaniac who wants to conquer the universe. Thanos (Josh Brolin) is a big guy with one big idea, that the universe is overpopulated. He reasons that if he kills half the people on every planet, there will be enough food for everybody. He doesn’t take into account that some planets are better at spreading out the resources than others. The 50 percent policy applies to all.

To that end, he sets out to gather the six stones of power that will give him the ability to exert his absolute will. (Tolkien got a whole trilogy out of one ring, but in Hollywood, nothing exceeds like excess.) And so we meet him, as he walks among fresh corpses, having just achieved stone No. 3. From there, the movie shows his effort to find the other three stones, including one that’s in the possession of Dr. Strange; another that’s conspicuously lodged in the forehead of Vision (Paul Bettany), and another that is at an undisclosed location known only to Gamora (Zoe Saldana), a guardian of the galaxy.

Hey, did you just skip that last paragraph? That’s OK. Forget it. Basically, “Avengers: Infinity War” sets up a pretext for several battles with several people in various locations. And the movie moves inexorably in a direction of those battles from its first minutes.

All the many characters get into the act, but not everyone has something to do. Chadwick Boseman as the Black Panther presides over a battle on his native soil, but probably speaks no more than a dozen lines in the movie and hasn’t a single important moment. Scarlett Johansson as Black Widow shows up in a number of scenes, but mostly just standing there. Meanwhile, Drax (Dave Bautista from “Guardians of the Galaxy”) has a couple of funny lines, and the film is a decent showcase for Elizabeth Olsen as Scarlet Witch, who spends a lot of the film worried about the jewel stuck in her boyfriend’s forehead.

Yet inevitably, when you have too many good guys, the villain becomes the star of the show. Two years ago, the writers of “Captain America: Civil War” came up with a decent solution to this by having the Avengers fight each other. But you can’t cart out the same trick twice.

As it stands, the field gets so crowded in “Avengers: Infinity War” that directors Anthony Russo and brother Joe Russo resort to letting Alan Silvestri’s score announce when something is important. If the horns are loud, it’s big. If the horns are louder, it’s bigger. If the horns are practically screaming, then it’s enormous. But is it? These are the horns that cried wolf.

It’s funny how the Justice League, DC Comics’ answer to the Avengers, has a completely different problem: Batman is powerless, and Superman is boring. And no one cares about anybody but Wonder Woman, so why give screen time to a succession of second stringers? “Avengers: Infinity War,” by contrast, dies of surfeit, not from lack, but it dies all the same.

Mick LaSalle is The San Francisco Chronicle’s movie critic. Email: mlasalle@sfchronicle.com Twitter: @MickLaSalle

Avengers: Infinity War

ALERT VIEWERAction. Starring Robert Downey Jr., Josh Brolin, Benedict Cumberbatch and Elizabeth Olsen. Directed by Anthony Russo and Joe Russo. (PG-13. 150 minutes.)

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