'21' hits a blackjack at the box office, March 28-30, 2008

Moviegoers hit the blackjack tables this weekend as Sony's film adaptation 21 knocked off two-week champ Horton Hears a Who for the top spot at the box office. Budgeted at a modest $35 million, the film shrugged off mostly poor reviews from critics (Rottentomatoes.com gave the film a rotten 32% recommendation rating) in bringing in an estimated $23.7 million over the weekend, averaging a top 10 best $8,950 in 2648 theaters. Adapted from the book "Bringing down the house" by Ben Mezrich, "21" is based on a true story about a group of MIT math wizes who devised a card counting scheme that took Vegas casinos for millions.

Starring Jim Sturgess, Kate Bosworth, and Kevin Spacey, the film was aided by a strong marketing campaign and an overall weak set of competitors, including MGM's Superhero Movie and Paramount's Stop-Loss. The film was star Kate Bosworth's second-biggest opening ever behind only 2006's Superman Returns with $52.5 million.

The lack of a big new debut plagued the box office for a second straight weekend, as the top 10 films found themselves down 25% from last year's comparable frame when Blades of Glory skated to the top spot with $33 million. It was down an even more discouraging 33% from 2006 when Ice Age: The Meltdown debuted with a record $68 million.

Two week champ Horton Hears a Who slipped just 29% to an estimated $17.4 million in second, bringing its 17 day total to a fantastic $117.3 million. As the first 2008 film to break $100 million, look for the Fox/Blue Sky animated comedy to finish with $160 million domestically.

MGM/Weinstein Company's spoof comedy Superhero Movie debuted softly with an estimated $9.5 million, averaging a weak $3,213 in 2,960 theaters. The poorly reviewed release fell well short of recent spoof comedies openings like January's Meet the Spartans ($18.5m), and 2007's Epic Movie ($18.6m), both Fox releases.

Paramount's teen comedy Drillbit Taylor fell a modest 44% to $5.8 million, bringing its ten-day cume to $20.6 million. Look for the film to finish with $30 million by the end of its run.

The studio's Iraq war drama Stop-Loss debuted in eighth with $4.5 million, averaging $3,505 in 1,291 theaters. Starring Ryan Phillippe as a vet recently returning home from war, the film received generally solid reviews from critics, but followed an existing trend of underperforming the Iraq War-themed films over the past two years.

A viewing outside of the top 10 was Simon Pegg's new comedy Run, Fat Boy Run, which took in a disappointing $2.4 million from just 1133 theaters. That comes out to a $2,109 per theater average for the poorly-reviewed Picturehouse release.

Check back next week for a look at how George Clooney's Leatherheads, Nim's Island and the horror pic The Ruins all fare.