This weekend, James Cameron’s science-fiction epic Avatar topped the box office for the third straight week, shooting past $1 billion worldwide, only the fifth movie ever to hit that mark. "It’s
like a runaway freight train. It just keeps doing business," said Fox
distribution executive Bert Livingston. "Here’s what’s happening: I
think everybody has to see Avatar once. Even people who don’t
normally go to the movies, they’ve heard about it and are saying, `I
have to see it.’ Then there’s those people seeing it multiple times." Finishing at No. 2 for the weekend was Robert Downey Jr.’s crime caper Sherlock Holmes, which has grossed $140.7 million after 10 days in theaters …