Reminds of an indie game called Iji. It's a platformer/shooter, but also combines puzzle elements where aliens destroy most of humanity because other aliens are trying to destroy them. There is a pacifist way to play the game, where you try to get around killing as few aliens as possible, and a not-so pacifist way. I would think that the more violent path in that setting would be more realistic, given the setting, but maybe that's because I got a "genocidal" kill rating the first time I played. [/end off topic]