It’s not easy to know how a Nicholas Cage-starring film is going to do at the box office.  His National Treasures movies have been boffo, but Bangkok Dangerous and Next were underwhelming to say the least.  That’s why most box office pundits, who predicted a close three-film race for box office supremacy this weekend, underestimated Knowing, the apocalyptic thriller from Summit Entertainment that easily topped the weekend chart with an estimated total of $24.8 million.  The Paul Rudd/Jason Segal “bromance” I Love You Man performed just about as expected, bringing in an estimated $18 million (Rudd’s Role Models opened to $19.2 million last year), while the Julia Roberts/Clive Owen thriller Duplicity slightly underperformed with an estimated $14.4 million.  Overall the weekend was down 5% from the same frame last year, marking the first two-week decline of 2009 so far—something that the debut of Monsters vs. Aliens next week should reverse.

Weekend Box Office (Studio Estimates): March 20-22, 2009

Last week’s winner, Race to Witch Mountain, dropped just 46.7% (a solid performance for an action film these days) and came in fourth with an estimated $13 million, while Watchmen continued its freefall with a 62.3% decline in its third weekend.  Watchmen, which features “unknown” superheroes and enjoyed an opening weekend roughly comparable to last summer’s Wanted,  is approaching $100 million domestically and has earned nearly $50 million abroad, but it now appears unlikely that it will reach Wanted’s domestic take of $134.5 million (and it certainly won’t come close to Wanted’s $207 million overseas haul).  Remember too, that Wanted was produced for $75 million, while Watchmen’s reported cost is in the $150 million range.  Since the studio’s average percentage take of a film’s domestic theatrical gross is 55%, it appears now that Watchmen won’t come close to making its cost back theatrically and will have to hope for solid DVD revenues to break even.

Other notable films in the top ten include the grisly horror/revenge remake Last House on the Left, which dropped 58% and finished sixth, the energizer bunny film of 2009 Taken, which declined just 37.6% and finished seventh in its eighth week of release, and Henry Selick’s adaptation of Neil Gaiman’s Coraline, which ended up in tenth place in its seventh weekend in theaters.

Knowing is another feather in the cap for the new indie studio, Summit Entertainment, whose prior effort Twilight was a major moneymaker.  Produced for $37 million, the teen vampire film earned $191 million domestically, and is likely to do extremely well on DVD (it was given a rare Saturday DVD release this weekend).  Knowing drew an older crowd (67% over 25), but appealed to both men and women with a 50/50 gender split.  If Knowing continues to perform like this, the odds are that the sequel-savvy Summit will find some way to turn this into a franchise just as Disney has done with the National Treasure films.

 I Love You Man attracted younger viewers as well as older fans, and with a solid CinemaScore of B+, this hetero "bromance" could demonstrate some serious legs over the coming weeks.