LOS ANGELES — Gatsby looks almost as great as a superhero at the weekend box office.

Leonardo DiCaprio’s “The Great Gatsby” partied like it was the Roaring ’20s with a $51.1 million debut that made it a surprisingly strong runner-up to comic-book blockbuster “Iron Man 3.”

Studio estimates Sunday put “Gatsby” at No. 2 behind Robert Downey Jr.’s superhero sequel, which pulled in $72.5 million domestically to raise its total to $284.9 million after just 10 days in U.S. theaters.

With an additional $89.3 million in its third weekend overseas, “Iron Man 3” lifted its international total to $664.1 million and its worldwide haul to $949 million.

“The Great Gatsby” far exceeded expectations by distributor Warner Bros. of a $35 million to $40 million opening weekend.

Director Baz Luhrmann’s 3-D adaptation of the F. Scott Fitzgerald classic was a rare box-office smash for films aimed at older adults during the youth-minded summer season. According to Warner Bros., viewers older than 25 made up 69 percent of the film’s audience.

The weekend’s other new wide release, Lionsgate’s romantic comedy “Peeples,” flopped at No. 4 with just $4.9 million. Produced by Tyler Perry, the movie stars Craig Robinson and Kerry Washington in a meet-the-parents-style farce.

Getting a head start on its domestic launch Friday, “Star Trek: Into Darkness” opened with $31.7 million in seven international markets. Its overseas debut included $13.3 million in Great Britain, $7.6 million in Germany and $5.5 million in Australia.

1. “Iron Man 3,” $72.5 million ($89.3 million international).

2. “The Great Gatsby,” $51.1 million.

3. “Pain and Gain,” $5 million.

4. “Peeples,” $4.9 million.

5. “42,” $4.7 million.

6. “Oblivion,” $3.9 million ($11.7 million international).

7. “The Croods,” $3.6 million ($17.3 million international).

8. “The Big Wedding,” $2.5 million ($2 million international).

9. “Mud,” $2.4 million.

10. “Oz the Great and Powerful,” $802,000.