One of the great gifts of the modern age of cinematic superheroes is seeing characters who were considered obscure, even by my fellow comic book fans back in the day, being turned into the stars of terrific films.

And one of the last superheroes I ever expected to receive the big-budget popcorn blockbuster treatment was the Big Red Cheese himself, “Shazam!”

Billy Batson (Asher Angel) is a teenage orphan in search of his mom in Philadelphia. He has run away from so many foster homes that the new family he’s placed with in the city is his last chance.

When he runs away after defending his disabled foster brother, Freddy Freeman (Jack Dylan Grazer) from a pair of school bullies, a ride on the subway mysteriously transports him to the chambers of a wizard (Djimon Hounsou) who needs a champion to defend the world from the Seven Deadly Sins that have been unleashed by the villainous Dr. Thaddeus Sivana (Mark Strong).

When Billy says the wizard’s name — “Shazam!” — he’s transformed into a lightning bolt-throwing superhero (Zachary Levi) in a grown adult body, and he turns to Freddy, a superhero-obsessed nerd, to teach him how to be a hero.

Look, there’s a lot of backstory that’s laid out in this film, even more than I’ve outlined here, but here’s all you really need to know:

This is basically Tom Hanks’ “Big” with superpowers, as is made explicit when the adult Billy and Sivana accidentally step on the oversized keys of an electronic floor piano during one of their hero-versus-villain punch-ups.

The joy of “Shazam!” comes from seeing a child get to live out all his fantasies, not just of having superpowers, but also being grown-up, and while Angel is a bit flat as 14-year-old Billy, Levi sells the heck out of the idea that his adult body is being piloted, and not always competently, by a giddy kid who’s constantly discovering the fun new stuff he can do.

Like Peter Parker, Billy also learns that, with great power, comes great responsibility, but perhaps more importantly, he realizes that real family isn’t determined by blood, but by those who stand by your side when you need them.

Strong tends to be the sort of generic villain actor you cast when you can’t afford Jason Isaacs, but you’ve budgeted for a bigger name than Colm Feore. Nonetheless, Strong actually does a decent job of capturing much of the clinical ruthlessness I’ve always enjoyed about Sivana in the comics. Even better, his mid-credits scene shows him striking up a partnership with one of my favorite comics mister— I mean, masterMINDS (hint for fellow comic book geeks).

Grazer continues the streak of scene-stealing performances begun in “It” and “Beautiful Boy.” Here, he gives such a painfully authentic performance as mouthy misfit Freddy, who wishes he could have Billy’s powers, that I felt like I was watching my adolescent self onscreen.

Fans of TV’s “Smallville” should appreciate seeing the always-engaging John Glover, a.k.a. Lionel Luthor, playing yet another heartless corporation-running father of a bald-headed supervillain.

And without spoiling too much, the rest of Billy’s foster family, who become a “Shazam family” of sorts, go from being initially saccharin and cloying to genuinely endearing.

This is not one of the more intellectually complex takes on the superhero concept, but I left the theater with a big, dumb grin on my face. Better still, it validates the notion that the best sort of hero is not the one who’s toughest, but the one who’s most kind.