After taking first place on Friday by just half a million dollars, the PG-13 thriller Unknown managed to strengthen its hold on the top spot despite the Saturday surge of the week-old family film Gnomeo and Juliet.  Once again, the estimates within the top five are pretty close, which means that these numbers are likely to change by the time the four-day President’s Day weekend wraps up on Monday night.

I have lost track of how many times this year I have had to begin this column with some variation on the sentence “overall, grosses are down over this period one year ago.”  How many weeks into 2011 are we now?  So yes, once again the studios have failed to find releases that are more appealing to American audiences than Valentine’s Day, The Wolfman and Percy Jackson: you know, the three big blockbusters of President’s Day 2010.  In fact, the combined total of this weekend’s three new titles is just barely above what Valentine’s Day made in three days all by itself.

None of which should tarnish the excitement of the team behind the number one Unknown.  Going into this weekend most people expected the Dark Castle/Warner Brothers release to lag behind the much-hyped teen thriller I Am Number Four.  These people had, perhaps, forgotten how Liam Neeson’s last thriller Taken had dominated over February of 2009.  Or perhaps they failed to notice how the trailer for Unknown was edited so that the word “Take” flashed repeatedly across the screen?

It was a smart campaign, especially as selling Unknown on its own (slightly convoluted) plot would have proved difficult.  This weekend’s top film has earned an estimated $21.8 million from 3,043 locations.  That’s not far below the $24.7 million debut of Taken but - recalling that the earlier film’s strength was its staying power over weekends two, three and four - the future for Unknown is far less certain.

The future of the I Am Number Four franchise, on the other hand, is fairly obvious. When the rights to the supernatural ‘young adult’ novel were picked up, the hope was that the property would translate into a Twilight-sized hit for the newly re-organized Dreamworks.  Promos for the film looked more like Village of the Damned than New Moon, however, and, despite coming close to the top spot on Friday, I Am Number Four could not quite get past the $20 million mark in its first three days.  With $19.5 million from its 3,154 locations, I Am Number Four looks like it will follow in the footsteps of Percy Jackson and the Olympians (just one of last year’s ‘young adult’ franchise hopefuls) and end up sans sequel.  Let’s hope those 2012 Alex Pettyfer calendars have not yet reached the printer.

I Am Number Four just barely edged out another film distributed by Disney: Gnomeo and Juliet.  Last weekend the all-ages animated film debuted at number three with $25.3 million.  At the moment the film’s estimate of $19.4 million means that Gnomeo lost just 24% of its debut audience.  It doesn’t hurt that the film is the only viable option for families, of course, but without any significant change in theatre count a hold like that is impressive.  In fact, expect to see I Am Number Four switch places with Gnomeo as the President’s Day weekend draws to a close.

Last weekend’s number one film Just Go With It also proved to have some staying power in its sophomore session, falling 40% and bringing its domestic total above $60 million in ten days.  Second week results for Justin Bieber: Never Say Never show that Bieber Fever cooled by approximately 54% in week two, putting the king of teen pop just outside the top five with an estimate of $13.6 million.  The 3D concert/biopic will move past the $50 million mark by Monday which is great news fr the studio if their $13 million budget figure is accurate.

Big Mommas: Like Father, Like Son grabbed the number five spot from Bieber with an estimated debut of $17 million from 2,821 locations.  The third release in the Big Mommas House trilogy (and who dreamed those words would ever be written) could not come close to the debuts of the first two films in the series ($25.6 million and $27.7 million, respectively) but who expected it to?  I consider it a victory that Martin Lawrence could get above $15 million considering that it has been five years since we last saw the man in his fat suit.

Unknown and Gnomeo may have the advantage again next weekend as both of the new releases set for theatres are rated R.  The Farrelly comedy Hall Pass has a screen count edge while the action flick Drive Angry has that 3D price advantage… and the disadvantage of starring Nicolas Cage.  So yeah, Hall Pass wins.  In the end look for me to trot out that now-familiar opening line yet again.