Who's the weakest superhero? At this summer's box office, so far, it's 'Green Lantern.' While Hal Jordan's power ring can conjure up just about anything, including a box office victory on opening weekend, the film's debut scared up only $52.7 million, according to studio estimates, marking the lowest opening of any of this summer's superhero sagas so far.

Expectations for the film had been a little higher, in the upper 50s, thanks to rising star Ryan Reynolds, a long-established fan base for the DC Comics character, 3D surcharges, and about a year's worth of hype. But the movie's reviews were poor and its word-of-mouth weak, and its emphasis on visuals over story and character may have contributed to this summer's ongoing box office backlash against superfluous 3D movies. So the film couldn't muster enough green energy to surpass the debuts of 'X-Men: First Class' (which opened with $55.1 million) or 'Thor' ($65.7 million.)
Last week's champ, 'Super 8,' fell to second place with an estimated $21.3 million. That's a moderate drop of 40 percent from a week ago, about what was expected, given the film's strong word-of-mouth and the direct competition from 'Green Lantern' for the same base of fanboys. In two weekends, the monster movie has scared up $72.8 million.

Premiering in third place was 'Mr. Popper's Penguins,' with an estimated $18.2 million. That's about what was expected, since the comedy was competing against the still-strong 'Kung Fu Panda 2' for the same family audience, it earned so-so reviews and its star, Jim Carrey, isn't the box office draw he used to be.

In its third weekend, 'X-Men: First Class' came in fourth with an estimated $11.5 million. It's down 52 percent from a week ago. In 17 days, the mutant movie has made $119.9 million.

At No. 5, 'The Hangover Part II' took in another $9.6 million, down 46 percent from last weekend. In four weekends of release, it's earned $232.7 million and is the highest-grossing movie of the year to date. Maybe 'Green Lantern' needed a cigarette-smoking monkey.

'Green Lantern' Trailer No. 2

The full top 10:
1. 'Green Lantern,' $52.7 million (3,816 screens), new release
2. 'Super 8,' $21.3 million (3,408), $72.8 million total
3. 'Mr. Popper's Penguins,' $18.2 million (3,339), new release
4. 'X-Men: First Class,' $11.5 million (3,375), $119.9 million
5. 'The Hangover Part II,' $9.6 million (3,460), $232.7 million
6. 'Kung Fu Panda 2,' $8.7 million (3,469), $143.3 million
7. 'Bridesmaids,' $7.5 million (2,573), $136.8 million
8. 'Pirates of the Caribbean: On Stranger Tides,' $6.2 million (2,742), $220.3 million
9. 'Midnight in Paris,' $5.2 million (1,038), $21.8 million
10. 'Judy Moody and the Not Bummer Summer,' $2.2 million (2,524), $11.2 million

Follow Gary Susman on Twitter @garysusman.
Mr. Popper's Penguins
Based on 30 critics

A man (Jim Carrey) turns his posh apartment into a winter wonderland after he inherits six penguins. Read More

Green Lantern
Based on 39 critics

A test pilot joins a band of warriors sworn to preserve intergalactic peace and justice. Read More