With Avatar the reigning champ and Sherlock Holmes still to come, Hollywood crossed the $10 billion line for the first time in U.S. and Canadian ticket sales for 2009.  Through Sunday, the total stood just $36 million short of crossing the $10 billion line, according to tracking firm Hollywood Box Office, and was set to plow across it Tuesday night.

The year’s top box office attractions were Transformers: Revenge of the Fallen and Harry Potter and the Half Blood Prince, and with hits like Harry Potter and The Hangover, Warner Bros. was the North American box office champ among studios.  And with both Robert Downey Jr.’s take on Sherlock Holmes and the return of those rascally rodents in Alvin and the Chipmunks: The Squeakquel coming in time for Christmas, the final take is expected to top $10.4 billion.

Hit the jump for a list of the top 20 domestic box office hits of 2009.