In Hollywood’s a dream factory, even the biggest filmmakers can find it difficult if not impossible to turn a dream into reality. This weekend sees the release of “Red Tails,” an action-drama about the Tuskegee Airmen during WWII. Producer George Lucas — “Star Wars” George Lucas — has been wanting to make the movie for over 20 years. Call them passion projects. “Red Tails” is the latest cherished story, but there are more on the way in 2012. Last year, Terrence Malick’s long-gestating project about the universe and a mid-’50s Texas family evolved into “The Tree of Life,” while Steven Spielberg and Peter Jackson collaborated as director and producer on “The Adventures of Tintin,” about a comics character that both hold dear.