"Leatherheads" a 1920s football comedy directed by Clooney, who co-stars with Renee Zellweger and John Krasinski had a soft opening of $13.5 million, below distributor Universal's expectations.
20th Century Fox's "Nim's Island" was right behind with $13.3 million. The family adventure centers on a bold girl (Abigail Breslin) alone on an island and her e-mail pen pal (Jodie Foster), an obsessive-compulsive, shut-in author.
"Leatherheads" and "Nim's Island" were so close that their rankings could switch after final weekend numbers are released Monday.
"Leatherheads" is Clooney's third directing effort, a commercial turn after his acclaimed Edward R. Murrow drama "Good Night, and Good Luck" and the Chuck Barris fantasy thriller "Confessions of a Dangerous Mind."
Yet "Leatherheads" earned mixed reviews and mainly drew theatergoers in their 30s and 40s, failing to connect with younger crowds that are the box office's mainstay, according to Universal.
"I'm disappointed for us, I'm disappointed for George. I think he's a great guy and think he's got tons of directing talent," said Nikki Rocco, head of distribution for Universal. "I wish I could have that crystal ball and tell you what went wrong."
He said some parents who might otherwise have gone to see "Leatherheads" may have been tied up taking children to see "Nim's Island" or the family hit "Dr. Seuss' Horton Hears a Who!"
20th Century Fox, which had been tracking "Nim's Island" slightly ahead of "Leatherheads," was pleased with the results of its film, said distribution executive Chris Aronson.
"This movie was targeted for families, and we hit the families," Aronson said of "Nim's Island."
Sony's "21," featuring Kevin Spacey, Kate Bosworth and Jim Sturgess in a Vegas blackjack romp, raised its 10-day total to $46.5 million.
Overall, however, it was another dreary weekend for Hollywood, where business has lagged nearly every weekend since January. The top 12 movies took in $80.9 million, down 27 percent from the same weekend last year.
Revenues are at $2.24 billion so far this year, off 1.8 percent from 2007, according to box-office tracker Media By Numbers. Factoring in higher ticket prices, movie attendance is running 5 percent behind last year's.
This weekend's other new wide release Paramount's horror story "The Ruins," about tourists who discover an ancient evil during a jungle trip debuted at No. 5 with $7.8 million.
In narrower release, Martin Scorsese's Rolling Stones concert film "Shine a Light," distributed by Paramount Vantage, did fair business with $1.5 million.
Wong Kar Wai's romantic drama "My Blueberry Nights," starring singer Norah Jones and Jude Law, Rachel Weisz, Natalie Portman and David Strathairn, took in a solid $73,742 opening in six theaters.
Estimated ticket sales for Friday through Sunday at U.S. and Canadian theaters, according to Media By Numbers LLC. Final figures will be released Monday.
1. "21," $15.1 million.
2. "Leatherheads," $13.5 million.
3. "Nim's Island," $13.3 million.
4. "Dr. Seuss' Horton Hears a Who!", $9.1 million.
5. "The Ruins," $7.8 million.
6. "Superhero Movie," $5.4 million.
7. "Tyler Perry's Meet the Browns," $3.51 million.
8. "Drillbit Taylor," $3.5 million.
9. "Shutter," $2.9 million.
10. "10,000 B.C.", $2.8 million.