Research shows that

Video Games make more money these days than movies. So, in a move that makes sense to someone in the Studio Chain, they want to tap into that market, and make movies based on them. For some strange reason, they think people will want to stop playing their games, and go see a movie BASED on the game they want to lure these people away from playing for 2 hours.

Let's suppose that the people playing the game can borrow their parent's car (or GET their parents to lend them the 10 bucks to go to a a movie and drop them off at the theatre), and remember how to get out of their parent's basement to actually FIND outside. What do they do when they get to the theatre? They aren't going to learn any Top Secret "exclusive moves to blast away aliens" or such. They'll sit wishing they were back playing the game.

And the other people that actually HAVE jobs, and don't have time for Video Games in their lives, what with knowing the secrets and pleasures of "outdoors"? Well they won't care about the movie.

DOOM will be Number one at the Box Office this weekend. I know this, and yet it doesn't change my opinion. Video Games are Interactive. Movies about video games aren't. The core audience eventually will realize that they could be at home BLASTING aliens, instead of watching other people blast them.

Or, maybe it will be a way to coax the gamers Outside and meet others of their kind.