'X-Men: First Class' lived up to part of its title. It opened in first place at the box office, but it's near the back of the class among the five X-films so far. The movie opened with an estimated $56.0 million, the weakest debut since the $54.5 million premiere of the franchise-launching 'X-Men' 11 years ago.

Each X-movie's opening seems to reflect audience satisfaction with the previous movie. 'X2: X-Men United' saw the figure rise to $85.6 million, while 'X-Men: The Last Stand" premiered with $102.8 million. Fans didn't like that one as much, so for 'X-Men Origins: Wolverine,' the number dropped to $85.1 million. And fans really didn't like that one, so this weekend's film opened even lower. In fact, it opened below what anyone had predicted.