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

Leonard 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 over 25 made up 69 percent of the film’s audience.

“It answers the question that you and I hear all the time from people over 50, ‘There’s nothing for me to see,”’ said Dan Fellman, the studio’s head of distribution. “While every studio has the $200 million tentpoles in the marketplace, you still have those who feel that it’s not directed at them, which is true. So that’s why I think counterprogramming like this is very important.”

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.