Last week, Adam Sandler and Jennifer Aniston -- stars of Sony's new comedy Just Go With It -- joked there was enough room at the box office for both them and teen icon Justin Bieber.

But the race turned out much closer than expected. According to weekend estimates, Go With It opened to an estimated $31 million from 3,548 theaters, while Paramount's Justin Bieber: Never Say Never far outpaced expectations in grossing an estimated $30.3 million from 3,105 locations, including 2,156 higher-priced 3D runs.

The race won't officially be called until Monday morning, when actual Sunday numbers are tallied, although most box office observers expect Go With It to retain the lead.

Never Say Never's cume is $31 million when folding in the $740,000 grossed from special screenings on Feb. 9. The performance of the hybrid biopic-concert film further solidifies Bieber's star status and the financial power of his girl-driven fan base.

Go With It is off to a solid start, but will need good legs over President's Day weekend. Sony also is expecting a spike tomorrow on Valentine's Day.

Overseas, the Sandler-Aniston film opened to $5.1 million from a handful of markets, including the U.K. and Mexico, for a global bow of $36.1 million.

Never Say Never and Go With It weren't the only victors of the weekend.

Disney's 3D family entry Gnomeo & Juliet did strong business in debuting to an estimated $25.5 million from 2,994 locations, scoring the best February opening for an animated pic (not a primetime month for toons). Rivals credit a strong marketing campaign for the film's success, as well as great reviews. Film came in No. 3.

Focus Features' Channing Tatum Roman epic The Eagle, the weekend's fourth new wide player, opened on the high end of expectations, grossing an estimated $8.6 million from 2,296 theaters to place No. 4.

Among limited openers, Fox Searchlight's comedy Cedar Rapids scored the best location average of the weekend. Pic grossed an estimated $310,789 from 15 theaters for an average of $20,179.

Back on the top 10 chart, Screen Gems' The Roommate held well in its second weekend, grossing an estimated $8.4 million for a cume of $26.1 million in its first 10 days. The thriller came in No. 5.

The Weinstein Co.'s awards frontrunner The King's Speech continued to succeed, coming in No. 6 and grossing an estimated $7.4 million for a domestic cume of $93.9 million. Film fell only 3%.

Although it looks to be the best weekend so far of 2011, the domestic box office still couldn't catch up with last year, partly because Valentine's Day fell on a Sunday in 2010. Revenues were down more than 25% .

The general malaise is part of the reason why Sony believes Go With It opened on the lower end for a Sandler pic. In 2004, Sandler romantic comedy 50 First Dates opened to $39.9 million, although it had the advantage of Valentine's Day falling on Sunday.

In the U.S., Go With It was marketed both to women and to Sandler's male fan base. The two-pronged approach seemed to pay off, with females making up 58% of the audience. Many of Sandler's films have played more to males, although females also made up the majority of the audience for the opening weekend of Grown Ups.

The romantic comedy played older, with 60% of those buying tickets over the age of 25. Overall, the film received an A- CinemaScore, in direct contrast to poor reviews. Females in particular liked the movie, giving it an A.

Go With It is the 11th Sandler film to open at No. 1 domestically, and cost $80 million to produce. Sandler's Happy Madison produced the romantic comedy, which was directed by the actor's longtime collaborator Dennis Dugan.

Sony worldwide president of distribution Rory Bruer said there was a lot of competition at the box office, citing Bieber's film in particular, but that Go With It held its own.

"It's a great start. Adam has again showed himself to be amazingly adept at understanding what audiences want to see," Bruer said.

Never Say Never was a wild card going into the weekend, since tracking services are notoriously bad at gauging concert films. Many box office observers thought the movie would have trouble cracking $20 million, and would take a bigger fall than it did on Saturday (pic grossed $12.4 million on Friday and $10.8 million on Saturday).

Film's opening came in just behind the $31.5 million opening for Hannah Montana/Miley Cyrus: Best of Both Worlds Concert Tour from 648 theaters, but Paramount insiders pointed out that Hannah Montana was billed as exclusive one-week run.

Girls flocked to see the Bieber movie, directed by Jon M. Chu (Step Up 2). Of those buying tickets to Never Say Never, 84% were females, while 67% were under the age of 25.

Never Say Never received an A CinemaScore overall, although females of all ages gave it a A+.

"One of the reasons the movie is playing so well is that moms loved it as much as kids," Paramount vice chair Rob Moore said.

Moore said moviegoers are responding to the fact that Chu and Bieber's team, led by manager Scooter Braun, crafted a film with a compelling storyline, versus making a traditional concert film.

Never Say Never could easily see a boost on Valentine's Day and President's Day weekend from Bieber's performance on Sunday night's Grammy Awards, as well as general word-of-mouth.

In terms of cost, Never Say Never's budget was a modest $13 million. Film was released by Paramount's Insurge Pictures, a low-budget arm looking to take advantage of social media. Never Say Never is a boon for Insurge.

The marketing budget for Never Say Never was half the cost of a normal spend, since Paramount relied heavily on forums like Twitter and Facebook to reach Bieber's fans. Movie's opening gross was as much as the production budget and marketing spend combined, according to the studio.

Gnomeo was the clear choice for families, who made up more than 72% of the audience. The toon, a leftover title from Miramax, featured music from Elton John, who personally helped publicize the film.

"Elton and the entire team who made the film must be thrilled," Disney worldwide president of distribution Chuck Viane said.

The Eagle was a favorite among males, of all ethnicities. Of those buying tickets, 38% were Caucasian, 27% were Hispanic, 21% were African American and 13% Asian.

Focus president of distribution Jack Foley said the film is in good shape financially, when factoring in the $8.6 million domestic debut and foreign presales (Focus parent studio Universal retained rights in English-speaking territories).

Focus wouldn't give the production budget, but insiders say it was in the low to mid $20 million range.

Like other companies, Focus is expecting good business over the long President's Day weekend.