Who would win in a fight, Batman or Superman? Could the Flash outrun Superman? Could Superman craft a boulder so heavy even he couldn’t lift it? While “Batman v Superman: Dawn of Justice” ostensibly seeks to tackle the first of those evergreen schoolyard hypotheticals, it’s the third that ends up proving the biggest litmus test for director Zack Snyder. Tasked with colliding the two most archetypal of American superheroes while also answering critics of his last outing, “Man of Steel,” and perhaps most importantly, paving the way for an extended DC Comics universe of films on which much of Warner Bros. future bottom line relies, Snyder has set a Sisyphean task for himself. That this very long, very brooding, often exhilarating and sometimes scattered epic succeeds as often it does therefore has to be seen as an achievement, and worldwide box office should be sufficiently lucrative to ensure future installments proceed on schedule. But amidst all the grueling work of saving the world and shouldering a franchise toward the heights, it would be nice to see these heroes, and this series, take a few more breathers to enjoy the view.

Proving that the placement of names in the title isn’t simply alphabetical, the first few reels of “Batman v Superman” are dominated by the Caped Crusader, with controversial casting Ben Affleck stepping quite comfortably into the role. That the film opens with yet another operatic depiction of the young Bruce Wayne’s most formative trauma is perhaps unavoidable — Thomas and Martha Wayne have been killed so many times in so many different media that their deaths may as well be one of the Stations of the Cross — but our first glimpse of the adult Wayne is hardly standard issue. Taking a civilian-level view of the cataclysmic destruction of Metropolis that ended “Man of Steel” on a contentious note, we watch as Wayne attempts to remotely evacuate his own Metropolitan Wayne Enterprises skyscraper, crippled by a wayward Superman (Henry Cavill) as he battles with General Zod just outside the frame. Despite his mad drive through the battle-torn streets, Wayne arrives just in time to watch, horrified, as a friendly security guard loses his legs and a young girl becomes an orphan.

Setting Wayne up as the film’s initial conscience is one of Snyder’s most interesting gambles, especially as his Batman quickly evolves into the most morally ambiguous iteration of the character yet seen on film. More than willing to shoot, brutalize and kill if the need arises, this Batman is still a figure of mystery in Gotham, and Snyder refrains from showing us the character in full cowl until surprisingly late in the game.

Fortunately, Affleck’s Wayne — here sporting salt-and-pepper temples and all the baggage of a man who, as faithful butler Alfred (Jeremy Irons) notes, “got too old to die young, and not for want of trying” — is a winningly cranky, charismatic presence even when out of costume. Diving headfirst into the sorts of detective work that Christopher Nolan’s Batman trilogy often short-shrifted, Wayne casts a skeptical eye on Superman while investigating a mysterious underworld figure named White Portuguese, his tracks traced by an equally mysterious woman (Gal Gadot).

Meanwhile, Superman has hardly recovered from the fallout of his chaotic battle with Zod when controversy strikes yet again. Though he’s been welcomed as a savior by most of Metropolis, in the course of rescuing Lois Lane (Amy Adams) from a terrorist interview gone awry, he’s blamed for the deaths of several African villagers. This attracts the scrutiny of the crusading southern Senator Finch (Holly Hunter), who heads up a Congressional Superman Committee, disturbed by the Krypton’s exercise of unilateral power.

She gains an uneasy ally in a cheeky young industrialist named Alexander “Lex” Luthor (Jesse Eisenberg, retaining his Zuckerbergian misanthropy from “The Social Network” and his stringy, Cobainian hair from “American Ultra”), who hopes to seduce her into allowing him to import a mysterious glowing green substance discovered in the Indian Ocean. Scarfing Jolly Ranchers, quoting Nabokov and showing up to formal events wearing a white blazer and sneakers, Eisenberg tackles Luthor as the brogrammer from hell, a chattily malevolent presence who provides the only real moments of levity in the film.

Juggling all of these strands while steadily beating the drum toward the battle promised in the title, Snyder sometimes loses track of his various allegories. Scripters Chris Terrio and David S. Goyer provide kernels of philosophical and theological quandaries throughout, while their nods toward contemporary political debates are more complex than the scattered visual gags (such as an anti-Superman protester waving an “Aliens Are Un-American” placard) might seem to imply. Yet the essential clash of ideologies promised by the central conflict — vigilante justice vs. self-sacrificing restraint, night vs. day, Dionysus vs. Apollo — never develops quite as forcefully as it should, and the life-or-death battle between the two icons ultimately comes down to a series of misunderstandings.

While “Batman v Superman’s” Dark Knight may be more of a pure punisher than some fans would prefer, Snyder’s conception of the character at least feels fully formed. Superman remains something of a work-in-progress. (If nothing else, it’s strange to see Clark Kent cast a more brooding figure than Bruce Wayne.) Daily Planet scenes are even more perfunctory this time around, and Adams’ Lois has plenty to do but little to say.

As a pure visual spectacle, however, “Batman v Superman” ably blows the hinges off the multiplex doors, and editor David Brenner does excellent work to comprehensibly streamline the chaos, capably captured by d.p. Larry Fong. Composers Hans Zimmer and Junkie XL are again key assets here, with Gadot’s theme in particular proving quite infectious. Snyder largely tamps down his penchant for hyper-stylized combat imagery until the end, when he stages a series of galactic battles that take style notes from sources as varied as classic WWE rumbles and Harryhausen creature features. As overblown as the lengthy showdown might become, Snyder gets closer than ever before to the chiaroscuro palette of classic comics, and even if his scrupulous efforts to avoid reopening “Man of Steel’s” collateral damage debates are a bit on the nose, at least he’s clearly received the message.