UPDATE 2-'Sex' less scintillating at box office

* "Shrek Forever After" retains crown in North America

* "Sex and the City 2" earns less than first film

* "Prince of Persia" dominates foreign box office (Updates with "Prince of Persia" leading world box office, and foreign sales data for "Sex and the City 2")

By Dean Goodman

LOS ANGELES, May 30 (Reuters) - "Sex" is losing its allure at cinemas.

The glamorous gals of "Sex and the City 2" were overshadowed by a green ogre at the weekend box office in North America on Sunday, as "Shrek Forever After" logged a second round as moviegoers' top pick.

Meanwhile, the new Walt Disney Co (DIS.N) adventure fantasy "Prince of Persia: The Sands of Time" was the No. 1 choice worldwide after coming in at No. 3 in North America and at No. 1 in 41 foreign markets. The weekend haul for the Jake Gyllenhaal vehicle stood at $89.2 million.

Comparisons between the "Shrek" and "Sex" sequels were a little dicey. "Shrek Forever After" earned an estimated $43.3 million in the three days beginning on Friday, while "Sex and the City 2" pulled in $32.1 million over the same period.

But the "Sex" sequel got a head start on the U.S. Memorial Day holiday weekend, opening on Thursday instead of the traditional Friday. Thursday sales of $14.2 million took the film's four-day total to $46.3 million -- which the ensemble comedy likely would have earned if it had opened a day later.

Still, the opening for "Sex and the City 2" fell far short of the three-day, $57 million launch for the first film in the series two years ago.

"Yes, I would love to have seen a bigger number, but I'm not concerned until I see how the second weekend plays out," said Dan Fellman, president of domestic distribution at the Time Warner Inc (TWX.N) unit.

He predicted the film would earn about $53 million once sales for the Monday holiday were included. Industry forecasters had expected the five-day haul to exceed $60 million.

PANNED BY CRITICS

Critics ripped the sequel, which reunites actresses Sarah Jessica Parker, Kim Cattrall, Cynthia Nixon and Kristin Davis with director Michael Patrick King.

Women accounted for 90 percent of the audience, up a few points from the first one. They also liked it a little less. The new film garnered a B-plus rating in exit surveys conducted by research firm CinemaScore, down from an A-minus, Warner Bros. said.

Internationally, the film grossed $27.6 million from 17 countries, led by Britain with $9.2 million and Germany with $7.3 million -- both more than 20 percent ahead of the first film, Warner Bros. said.

DreamWorks Animation SKG Inc's (DWA.O) "Shrek Forever After," which also suffered a disappointing debut last weekend, held up surprisingly well. Sales slipped just 39 percent, a better hold than the 56 percent drop for "Shrek the Third" in 2007.

The North American tally for the cartoon stands at $133.1 million, down from the comparable 10-day haul of $203 million for "Shrek the Third." The studio, whose films are distributed by Viacom Inc's VIAb.N Paramount Pictures, said it was too early to tell if the new film could catch up.

The film has also earned $53.8 million from 15 foreign markets. Russia has contributed $38.5 million.

"Prince of Persia: The Sands of Time" earned $30.2 million in the United States and Canada. Disney forecast the film would earn about $37 million after Monday, in line with industry forecasts. The international total was $59.0 million from 47 countries. Since the film got an early start last weekend in 19 markets, its tally stands at about $118 million.

(Editing by Sandra Maler and Cynthia Osterman)