Spurred by the success of “Batman Begins,” ”Spider-Man,” “Iron Man,” “X-Men” and their sequels, superhero blockbusters have become a cinema staple in the last decade. “Thor,” based on the Marvel comic book inspired by Norse myth, arrives in theaters May 6, and “Green Lantern,” “Captain America: The First Avenger” and “X-Men: First Class” follow later this summer.