Why not base a movie on one of the best selling novels based on the game, no?
Honestly, I don't want them to do that for a few reasons.
The biggest one is that it is really hard to translate a story from one medium to another. Almost every movie made out of a book series gets shredded and destroyed in the process. Think about Eragon, a pretty great series (in my opinion, I haven't read it in years) that created a single movie that destroyed everything it touched.
Even the best movies, like the Harry Potter movies or the LoTR movies are often talked about with what they changed and/or got wrong than how great they were.
So, I think we are far better off getting a movie tha takes the property, and makes a unique story no one has published before. Because then we are less likely to get lambasted for the things they got wrong from the original story.
Still going to get blasted for getting the setting, mechanics, look, ect wrong. But we can at least avoid that with the story.