4 stars, Rated PG-13 (134 minutes) Marvel films pop up with the regularity of iTunes updates, so it’s hard to fault even the most dedicated fans for feeling desensitized to their charms. “The Black Panther,” Marvel’s 18th big-budget comic-book adaptation since 2008, vaults over all of them to become not only the best of the Marvel Cinematic Universe — rivaled only by “Guardians of the Galaxy” — but also one of the most groundbreaking and blood-tingling comic-book flicks of all time. To mangle an oft-quoted line from Christopher Nolan’s “The Dark Knight,” it’s not simply the film audiences need and deserve, it’s the one for which an entire industry has been crying out. Black superheroes are not groundbreaking in 2018, of course.