LOS ANGELES (AP) — Tony Stark piloted to the top of the box office but not the record books.

Iron Man 2, the sequel starring Robert Downey Jr as the gadget-happy billionaire superhero, earned $133.6 million domestically on its opening weekend, according to distributor Paramount Pictures’ estimates yesterday. The opening rocketed past the original $98.6 million debut in 2008 and landed the record as the fifth-biggest opening weekend.

Iron Man 2 has taken in $194 million overseas since it debuted in many international markets last week, bringing its worldwide total to over $327 million. While Hollywood blockbusters typically open around the same date in most countries, some get an overseas jump of a week or more on their US debuts. The biggest opening came from China with $7.3 million.

“It’s a perfect kickoff to the summer of 2010,” said Paul Dergarabedian, box office analyst for Hollywood.com. “It literally sets the tone for the entire summer movie season. To have the fifth biggest opening week of all time certainly sends a message that this summer season is going to make its mark. Audiences really do get caught up in that.”

The victory of Iron Man 2, which is only available in 2-D, comes at time when 3-D films like Avatar and Alice in Wonderland have recently dominated the box office. IMAX chairman and president Greg Foster said the $10.2 million earned by Iron Man 2 from IMAX theaters set IMAX’s 2-D record, beating out the $8.5 million debut of Star Trek last year.

The film continues the story of Stark, a genius industrialist who builds metal suits loaded with gadgets. In the follow-up, the superhero employs the assistance of his longtime friend and fellow crime fighter James Rhodes, played by Don Cheadle, to battle baddies such as Whiplash, a nasty villain with his own high-tech arsenal, played by Mickey Rourke.

“When we opened the original Iron Man, it seemed to be one of the lesser known properties in the Marvel galaxy,” said Paramount’s Harris. “Two years later, it’s one of the most beloved characters. I think the people at Marvel are incredibly bullish about how future Iron Man movies might do and how Iron Man interacts with their other characters.”

Despite the triumph over its predecessor,Iron Man 2″ didn’t best the $158.4 million bow of The Dark Knight in 2008 or the $151.1 million debut of Spider-Man 3 in 2007. It also didn’t surpass last year’s $142.8 million dawn of The Twilight Saga: New Moon or the $135.6 million course charted by Pirates of the Caribbean: Dead Man’s Chest in 2006.

Iron Man 2 was untouchable at this weekend’s box office though. The previous weekend’s No 1 movie, the Warner Bros. remake of A Nightmare on Elm Street, fell to No. 2 with $9.1 million, clawing to a total of $48.5 million. DreamWorks Animation’s How to Train Your Dragon remained at No 3 with $6.7 million, bringing its seven-week total to $201 million.

Babies, the Focus Features documentary that tracks four tots during the first year of their lives, was the only other new release, debuting in 534 theaters at the No. 10 spot with $1.5 million. Hollywood.com’s Dergarabedian said Babies could continue to crawl along this summer as an alternative to flicks like Robin Hood and Prince of Persia.

Estimated ticket sales for Friday through Sunday at US and Canadian theaters, according to Hollywood.com; final figures will be released today: