2. X-Men: Days Of Future Past
The penultimate spot on our list goes to X-Men: Days of Future Past. The story deals with the X-Men trying to prevent a future dystopian reality in which huge robotic Sentinels rule the United States. In this future, mutants are being hunted down thanks to an event in the present. The timeline alternates between the then present 1980s and the (now) past 2013. The mutants in the future are living in fear of an impending nuclear holocaust, perhaps inspired by the fact Days of Future Past was written during a period of elevated tension in the cold war. The remaining X-Men in the future band together and send an adult Kate Prydes mind back into her teenage self in a final bid to change the past and save the future. As well as spawning a sequel, X Men: Days of Future Present, the story is important to the X-Men timeline as it see Rachel Summers, the daughter of future versions of Cyclops and Jean Grey, traveling from the future to the to join the X-Men of the present. She is also followed through time by a powerful Sentinel, Nimrod, who will become a nemesis of the X-Men throughout later story arcs. This is definitely one to read for any X-Men fan.