The only way to save someone who's just been hanged is to lift him from his legs gently to loosen pressure on his neck. This rarely works and must be done right after the person has been hanged, supposing that his neck held when the rope snapped. Do not touch his neck, lay him on the ground and administer CPR.
In video games, hanging can appear as a plot point or as part of the historical context of the setting. It can also be used to add atmosphere, especially in the horror genre. There's nothing creepier than seeing a row of hanged people.