Realism is not always neccesary, you just have to make everything plausible in the universe you created.
For instance: Faster than Light-travel is impossible, but Mass Effect gives you technology that makes it possible. As long as it does not contradict with what you created before this is plausible within the universe of Mass Effect.
For instance: Faster than Light-travel is impossible, but Mass Effect gives you technology that makes it possible. As long as it does not contradict with what you created before this is plausible within the universe of Mass Effect.