Updated from 11:46 a.m. EDT with additional details about weekend box office revenue.By David Germain, AP Movie Writer 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 its distributor, Warner Brothers ( TWX), 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 Brothers, viewers over 25 made up 69% 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 ( LGF) 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. Starring DiCaprio in the title role as 1920s mystery millionaire Jay Gatsby, the latest Fitzgerald update co-stars Carey Mulligan as his lost love and Tobey Maguire as the friend chronicling their doomed romance. It was by far the biggest debut ever for Luhrmann, whose previous best was $14.8 million for Australia. In just one weekend, The Great Gatsby nearly matched the $57.4 million domestic haul that Luhrmann's top-grossing film, the musical Moulin Rouge!, managed in its entire run.