In terms of effect on the Marvel Universe/characters and Marvel's storytelling in general, what is the most influential? a few popped to mind, including Galactus's first "visit" to Earth, Phoenix saga, and Norman Osborne as Green Goblin, but my pick is... Days of Future Past It established a sense of impending doom for the universe, surrounding the mutants. And though there was time travel before (see Kang), this storyline laid the groundwork for Cable, Bishop, House of M, Age of Apocalypse, etc. with alternate timelines. What do you think?