As franchise firsts go, Paramount’s “Thor” ranks as one of the best: Its estimated $66 million opening is the third-highest series launch for Marvel behind “Spider-Man” and “Iron Man.”

“Thor’s” domestic debut is, however, a far cry from the thunderous $128 million openingearned this time last year by fellow Marvel entry “Iron Man 2.”

“Thor,” which collected 60% of its domestic bow from 2,737 3D screens out of a total 3,955 locations, also stands as the year’s second-best domestic opener behind last weekend’s “Fast Five.” With an added overseas weekend take of $46 million, the global cume has reached a boffo $242 million in just 11 days.

The domestic opening well exceeded Par’s original expectations based on openings for similar Marvel pics like “X-Men,” “Fantastic Four” and “The Hulk” — all of which “Thor” already has outgrossed overseas. But “Thor” performed in line with what most other pre-weekend tracking services had projected — a launch north of $60 million.

That pic’s lofty benchmark ultimately was too high even for the combined B.O. might of “Thor” and Universal soph player “Fast Five” to match, leading to a weekend that was off approximately 11% vs. the same frame in 2010.

“Fast Five” dropped an estimated 62% — typical of similar franchise installments, but by no means desirable — grossing another $32.5 million for a Stateside cume to $139.9 million. That makes “Fast Five” this year’s most successful film so far domestically, and with an added $185 million offshore total, worldwide cume is $325 million.

Despite two major tentpoles in the market, the weekend’s pair of femme-driven counterprogrammers, Sony’s “Jumping the Broom” and Warner Bros.’ “Something Borrowed,” both debuted well to their core audiences, with an estimated $13.7 million and $13.2 million, respectively.

“Jumping the Broom,” boosted by a strong faith-based component, exceeded weekend projections, especially considering most B.O. pundits had predicted the Sony pic to land behind “Something Borrowed,” which debuted in line with industry expectations.

“We found that the picture had a much broader appeal than to just faith-based audiences,” said Sony distribution topper Rory Bruer.

Thanks to manageable production costs, both pics are likely headed toward profitable runs over the next few weeks given that female-targeted films usually play best during weekdays.

Not so fortunate, however, was Summit’s limited launch of Jodie Foster-Mel Gibson starrer “The Beaver,” which kickstarted its domestic run this weekend at 22 locations, averaging a mere $4,745 per screen.

The film cost a reported $21 million, but thanks to considerable foreign pre-sales, Summit, along with Participant Media and Imagenation Abu Dhabi, have limited vested interest in the film. Summit plans to expand “The Beaver” domestically on May 20, after it screens at the Cannes Film Festival. Pic’s international rollout is slated to happen over the coming months.

With “Thor” poised to attract plenty of male moviegoers (it skewed 63% male), one of the weekend’s biggest question marks was how well U’s male-driven “Fast Five” would hold in its second outing.

Last weekend, “Fast Five” earned 56% of its $86 million opening from male audiences, though a more significant portion of that (65%) came from ethnic auds. “Thor” had been tracking strongest with both groups for several weeks leading up to its release.

But unlike “Fast Five,” which played best with auds under 25, “Thor” tallied most of its opening from those over 25, with 72%. That demo gave the film a B+ CinemaScore rating, comparable to the pic’s overall rating, while moviegoers under 25 rated the film better with an A-.

Par vice chairman Rob Moore said the better score with younger auds means good news for “Thor” as it plays through the next few weeks of summer.

“The tendency for films with sci-fi elements is to start playing younger once school holidays start,” he said. “Those films usually start older but play best with younger audiences.”

The pic’s potentially younger crowd also lends itself to increased 3D grosses, since under-25 auds are most open to the format.

“Thor” opened better than similar major tentpole “Tron: Legacy,” with $44 million, but earned less from 3D. “Tron” (shot in 3D) saw 82% of its opening come from the premium format, compared to “Thor’s” 60% 3D share (latter pic had a post-production conversion).

Mother’s Day boosts

Concerning the weekend’s 2D debut pair, both “Jumping the Broom” and “Something Borrowed” received positive ratings from their core audiences. “Broom,” which played to 70% female, scored an A CinemaScore rating, while “Something Borrowed,” with 73% female turnout, received an overall B rating.

“It’s a nice female-oriented film that should be around for a while,” said Warners exec VP of distribution Jeff Goldstein, who added that “Something Borrowed,” along with “Jumping the Broom,” should benefit most from mother-daughter duos visiting the multiplexes on Mother’s Day.

Twentieth Century Fox’s 3D toon holdover “Rio” likely will see the most family traffic on Sunday, with Fox estimating $8.2 million for the film, down 45% in its fourth frame. “Rio” has a Stateside total of $114.9 million, with an international cume nearing $300 million.