Anyone can be a superhero these days:

Once upon a time, a movie poster needed to have only two words on it: the star’s last name and the title. Stallone: Rambo. Schwarzenegger: Terminator. In the new action-hero economy, though, actors rarely carry the franchise; more often, the franchise carries the actor. Chris Hemsworth was little known before “Thor,” and no one outside the industry was too familiar with Henry Cavill before “Man of Steel.” Lorenzo di Bonaventura, who produced “Transformers” and this winter’s “Jack Ryan: Shadow Recruit,” told me that studios were gambling on unproven actors for economic reasons. “These movies cost a lot to mount. Adding on the big movie star’s salary is the thing that makes you go, ‘Boy, I don’t know if I can afford it.’ ” Perhaps no movie typifies this model better than the 2006 mega-hit “300,” an adaptation of Frank Miller’s popular comic-book series, which featured inexpensive and little-known actors like Gerard Butler and Michael Fassbender and then catapulted them to stardom. This week, the film’s producers are trying to replicate that success with a sequel, “300: Rise of an Empire,” which is anchored by the unheralded Sullivan Stapleton and 299 other equally fit, anonymous men in leather skirts.