I feel like this could be a great movie... if you haven't played Mass Effect. The main problem with game adaptation movies is that it takes something personal, something which you helped to create, and comes up with a different version of it. With a game like Call of Duty, it won't be that noticeable: a few action sequences will be different, but it'll generally be the same cast of characters with or without you. The problem with Mass Effect (and many other RPGs) when it comes to film adaptations is that they rely so heavily on player choice. It's jarring enough to watch the story unfold under someone else's decisions, with characters living or dying in a potentially very different way from the way you think it should be, so a film adaptation will only further shock players when 'dead' characters (by which I mean the ones who didn't make it to the credits on your playthrough) survive.
That said, I have high hopes for this. Apparently, members of the BioWare team are onboard with this, and that will help to avoid the collapse of the plot into a mindless cash-in on a popular franchise. Also, anyone who HASN'T played the games could come to see gaming as a medium with well developed universes, characters, and plots--all too often I find myself telling ignorant dumbasses that yes, games do have plots, and no, they're not just mindless gratuitous violence. I don't expect an ME movie to bring the mainstream out of their ignorance and into the bliss of gaming enlightenment, but it could certainly help if well executed.
In summary, I'm reservedly excited for this, and I suppose that I'll be going to see this when it comes out, for better or for worse.