If we know the in-game "killing" isn't real, will this create any negative karmic effects?
I guess there may be two problems with it:
- It may be unlikely to create positive karmic effects -- I think that positive karma is associated with wealth and ease and so on -- see for example Sigalovada Sutta (DN 31) for an example of some of the Buddha's advice for lay-people (I remember it as the sutta of the "six directions").
It may be (which I think is what RuthLydia's answer was saying) an activity that not associated with progress towards the ending of karma.
I guess that playing video games is associated with sensual craving -- craving ongoing sensual stimulation.
Instead perhaps you're supposed to find peace in the "unconditioned" ("unconditioned" meaning "doesn't have a cause") -- or possibly something to do with, beginning with, conditioned by, virtues (perhaps "good deeds" or "skilful" actions).
Also it might be worth mentioning the "Brahma-viharas" which are said to be, "the answer to all situations arising from social contact". Assuming that video games are a type of social contact, perhaps they're unskilful to whatever extent that they don't involve the Brahma-viharas (i.e. developing "good will" towards people, and so on).
As for movies, there's a sutta addressed to an actor (SN 42.2) which warns against acting, for which it reasons:
Any beings who are not devoid of passion to begin with, who are bound by the bond of passion, focus with even more passion on things inspiring passion presented by an actor on stage in the midst of a festival. Any beings who are not devoid of aversion to begin with, who are bound by the bond of aversion, focus with even more aversion on things inspiring aversion presented by an actor on stage in the midst of a festival. Any beings who are not devoid of delusion to begin with, who are bound by the bond of delusion, focus with even more delusion on things inspiring delusion presented by an actor on stage in the midst of a festival.
In other words, what's presented on the stage in a festival will tend to increase the Three poisons (i.e. desire, aversion, and ignorance).
From a hypothetical perspective, are these cultures being carefully prospered by the ruling class of this planet to keep individuals chained to Samsara for as long as possible?
I think you tend not to blame other people for your own lack of progress (e.g. "It's not my fault, it's his fault that I'm chained to samsara!").
When there is an opponent to enlightenment, an enemy, that's often portrayed as being Mara.