On some level, roughly 98 percent of all videogames are about the end of the world. There's always some supervillain/monster/alien race who's threatening to conquer the Earth or blow up the galaxy, and it's up to you to stop him/her/it/them. For all the games that use end-of-the-world scenarios to drive their plots, though, how many actually don't let you avert the apocalypse? The end of the world is always a potent threat, but it's even more potent when you have to sit there and watch it unfold. GamesRadar takes a look at the top 7 games which do this the best.