Many people would tend to define writing as the single factor that can generate a plot in a video game. I know that we've kind of stepped away from that notion here, but there are several assets that define narrative in video games:
- General Aesthetic
So I'd like to bring up a somewhat story oriented game franchise in which this doesn't work that well, Halo. Master Chief and to a slightly lesser extent Noble Six play as really odd characters. They aren't necessarily written badly, but their downfall is ultimately more gameplay related. I want you to put yourself in their shoes for a second: they were kidnapped and genetically modified to be part of a war effort, one that, at that point, didn't even involve aliens. From that point, their singular purpose in life was to kill. While the story sometimes reflects on that, such as the opening cutscene in Halo 4, the gameplay really doesn't show any of that. You show no emotion while killing anything in that game, nor do you show any sociopathic tendencies as that cutscene hints at. You just kill things.
I'm not throwing Halo under the bus. I'm not really even saying that it needs to do this; a fun shooter really doesn't need perfect consistency to be a fun shooter. It's just a game I've played a lot of. One could easily say the same about Half Life, or anything like that. In reality, there are very few games that nail this. The only three I can think of off the top of my head are Hotline Miami, Spec Ops: The Line, and the Portal franchise.
I guess what I'm trying to get at here is that a plot-centric game should have at least some balance. And there are really to ways to do this: you can have the player affected by the violence like in Spec Ops or Hotline Miami, or you can choose different focuses, other than violence, that may be easier to implement because they don't have quite the emotional weight on a normal person as violence does. I'm not trying to condone violence in games as something bad, I'm just saying that if you want to put violence in a heavily story centered game, at least add some weight to it.