'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.

Those predictions were all over the place, from $58 to $72 million, figuring that the venerable comic title still has a lot of residual good will, and that competition from fellow Marvel superhero flick 'Thor' had just about played out after a month in theaters. Besides, there were no other new wide releases this week, and reviews were generally positive. On the other hand, 'First Class' didn't have the advantage of 3D or IMAX surcharges, and this prequel's plot lacked enough appeal beyond the fanboy set, whose interest in an origin story would outweigh the movie's absence of familiar characters like Wolverine or the usual ensemble of well-known actors. (The movie's best-known star is villain Kevin Bacon.)

Also falling even lower than predicted was 'The Hangover Part II.' After last weekend's record-smashing holiday blowout, a big dropoff of 50 to 55 percent was expected, especially since 'X-Men' was chasing some of the same young male audience, and since word-of-mouth on 'Hangover II' is so polarizing. (People either loved that it was so much like the original or were bored for the same reason.) In fact, the comedy sequel dropped a full 62 percent, to an estimated $32.4 million. Still, the movie has earned a stunning $186.9 million in 11 days (plus another $60.3 million overseas), so its smash status is hardly diminished.

Last weekend's other big opener, 'Kung Fu Panda 2,' also experienced a big drop, almost 50 percent, to an estimated $24.3 million. That was expected, since last weekend was a holiday, promising a bigger kid audience. Still, that was enough to pass the $100 million mark, after 11 days. At this rate, 'Panda 2' has a chance to become the biggest animated hit of the year to date, at least until 'Cars 2' opens in three weeks.

In fourth place, after another steep plunge (55 percent), was ''Pirates of the Caribbean: On Stranger Tides,' with an estimated $18.0 million. The movie is still playing on 3,966 screens, more than any other current film, so it will still have legs for a while, even if they're as wobbly as Captain Jack Sparrow's. In three weekends, it's earned $190.3 million, plus another $536.7 million overseas, for a total of $727.0 million worldwide. That's some serious booty.

Rounding out the top five was 'Bridesmaids,' with another estimated $12.1 million, down a modest 27 percent in its fourth weekend. The all-female ensemble comedy crossed the nine-figure mark this week, for a total to date of $107.3 million.

On the indie front, 'Midnight in Paris,' continued to expand, taking in another estimated $2.9 million, up 51 percent from last weekend and good for an eighth-place finish. The Woody Allen comedy enjoyed the highest per-screen average of this week's top 10 movies ($19,837, compared to $15,380 for 'X-Men').

Also scoring big on a handful of screens were 'The Tree of Life' ($31,050 average on 20 screens, for an estimated total of $621,000 for the weekend and $1.3 million over ten days of release) and new release 'Beginners' ($27,000 on each of five screens, for $135,000 total). In fact, the per-screen average for the critically acclaimed Ewan McGregor-Christopher Plummer dramedy is so high that there's talk it could be this year's 'The Kids Are All Right' (another crowd-pleasing, button-pushing indie fave with a gay twist) once it expands to a wider release.

Overall, this weekend's box office was up 26 percent from the same weekend last year, a weekend so lackluster that 'Shrek Forever After' spent its third session in a row at No. 1 with just $25.5 million, beating newcomers 'Get Him to the Greek' and 'Killers.' For the year to date, however, the total box office is $4.1 billion, down 7 percent from this time last year. There's still a lot of work to be done to make up for the slump that dominated the first three and a half months or so of 2011.

'X-Men: First Class' Trailer No. 2


The full top 10:
1. 'X-Men: First Class,' $ 56.0 million (3,641 screens), new release
2. 'The Hangover Part II,' $32.4 million (3,615), $186.9 million total
3. 'Kung Fu Panda 2,' $24.3 million (3,952), $100.4 million
4. 'Pirates of the Caribbean: On Stranger Tides,' $18.0 million (3,966), $190.3 million
5. 'Bridesmaids,' $12.1 million (2,919), $107.3 million total
6. 'Thor,' $4.2 million (2,780), $169.1 million
7. 'Fast Five,' $3.2 million (2,237), $202.1 million
8. 'Midnight in Paris,' $2.9 million (147), $6.9 million
9. 'Jumping the Broom,' $0.87 million (589), $35.9 million
10. 'Something Borrowed,' $0.84 million (688), $36.7 million

Follow Gary Susman on Twitter @garysusman.