Paramount and Marvel Studios scored another victory as Chris Evans-starrer Captain America: The First Avenger topped the domestic box office with an estimated $65.8 million launch, in line with fellow superhero pic Thor and successfully priming the audience for next summer’s superhero extravaganza The Avengers.

Technically, Captain America is the highest grossing superhero pic of the summer, having narrowly beat the $65.7 debut of Thor, but even Paramount insiders cautioned  Sunday's estimate of $65.8 million could turn out to be too high, meaning Thor will come out ahead.

Captain America did enough business to come in No. 1, ahead of Harry Potter and the Deathly Hallows Part 2, which fell a steep 72% after its mammoth debut a week earlier.

Warner Bros.' Deathly Hallows 2 still remained a box office giant, grossing $48.1 million in its second frame for a domestic total of $274.2 million. Its dip was no surprise to box office observers, considering it opened to $169.2 million, the best showing of all time and underscoring the rush to see the final title in the franchise. The pic is destined to become the top earner of the series, and is already close to eclipsing the $317.6 million earned domestically by Harry Potter and the Sorcerer's Stone.

Deathly Hallows 2 easily won the weekend race at the international box office, grossing an impressive $121.3 million in its second weekend--a 61% drop--for a foreign total of $560.4 million and massive global cume of $834.6 million as the pic races toward the $1 billion mark.

Coming in No. 3 at the domestic box office was Screen Gems’ Justin Timberlake-Mila Kunis starrer Friends With Benefits, Hollywood’s latest raunchy R-rated comedy. The pic, directed by Will Gluck, opened to $18.5 million, slightly behind the $19.7 million earned by the similarly themed No Strings Attached in January of this year.

Friends With Benefits, made for a modest $34 million, played best to women, who repped 62% of the audience, and drew a B+ CinemaScore

The Screen Gems film will need a good hold if its to overcome the lowest opening among the recent crush of R-rated comedies. Sony worldwide president of domestic distribution Rory Bruer believes Friends With Benefits will accomplish exactly that.

"This film will be around for the rest of the summer. The chemistry between Justin and Mila is great," Bruer said.

Released in 3D and directed by Joe Johnston, Captain America was the main headline of the weekend. Together, Captain America and Thor—which opened to $65.7 million in May—sport the biggest openings of the summer for non-sequels, and the best of any superhero pic. It easily bested the $53.2 million debut of Green Lantern. However, Captain America only drew 40% of its grosses from 3D screens, a far lower ratio than Thor.

Captain America, receiving an A- CinemaScore, did drew a younger audience than Thor, with 43% of those buying tickets under the age of 25. Of those turning out for the opening weekend of Thor—which drew a B+ CinemaScore—only 25% were under the age of 25.

Costing a reported $140 million to make, Captain America is the final title to be distributed theatrically by Paramount per its deal with Marvel Studios. Together the partners have now released four films, including the first two pics in the enormously lucrative Iron Man franchise.

Disney, owner of Marvel, will now take over the distribution of Marvel titles previously handled by Paramount, although Paramount will still have an interest in Avengers and Iron Man 3, including pay TV rights.

Both Chris Evans and Chris Hemsworth, star of Thor, are reprising their roles in Avengers, which also features Mark Ruffalo as The Incredible Hulk and Sam Jackson. as Nick Fury, among other Marvel characters.

“When you look at these two properties [Captain America and Thor], you’ve now got a lot of momentum going into next summer’s Avengers,” Paramount vice chairman Rob Moore said.

Even rival studios have credited Paramount for its marketing acumen.

Captain America and Thor have done the best of any superhero pic this summer in terms of their opening gross, while Thor is the summer’s top superhero title worldwide, grossing $445.8 million globally, compared to the $346.9 million earned so far by Fox’s X-Men: First Class.

There have been questions about how Captain America will perform overseas, because of its title and bent. If the film’s opening in Italy over the weekend is any indication, the movie appears to be on solid footing.

Captain America opened to $2.8 million in Italy, 16% ahead of the first Iron Man, but slightly behind Thor.

“It played like a big tentpole in Italy, suggesting there won’t be much push back overseas,” Moore said.

At the specialty box office, the Weinstein Co. was the big winner as Kristin Scott Thomas French drama Sarah's Key grossed $117,000 as it opened in five theaters in New York and Los Angeles for a per location average of $23,409, the best of the weekend. The film, acquired by TWC at the 2010 Toronto Film Festival, will expand into 17 additional markets this coming Friday.

Fox Searchlight's new entry Another Earth opened in four theaters in New York and Los Angeles, grossing $78,413 for a per location average of $19,600. The sci-fi/fantasy marks the directorial debut of Mike Cahill, and was acquired by Searchlight at the 2011 Sundance Film Festival, where it was a festival darling. Searchlight takes the film into 20 new markets.

All told, domestic box office revenues were up as much as 18% this weekend over the same frame last year, when Salt and Romena and Beezus were the new offerings.