The abundance of movies and television programs may have something to do with this. Instead of fighting it you can use this situation as a tool to get your kids reading. Find out if it was based on a book. Many of the popular kids films are based on story books and novels. Their curiosity and interest should be sparked after viewing the film.
Many kids prefer to read something which, in their opinion, is safe.
In other words, something they are guarenteed to like. One benefit of reading a book they've previously enjoyed as a film is the familiarity of the characters. Kids like to know what they're going to get. Characters they already feel sympathetic towards are a necessity in reading enjoyment. It's like taking a short cut.