According to the Hollywood Reporter, production company Legendary Pictures has picked up the rights to Mass Effect. Legendary is responsible for the latest Batman reboot and the recent Watchmen movie. The film is set to be produced by Avi and Ari Arad and written by Mark Protosevich, who worked on I Am Legend. Rights to movies get bought up all the time, so this is in no way a confirmation of a Mass Effect movie being made, but just that it is a possibility.
