The X-Men are Marvel's most successful team of superheros. And that is actually surprising if you know a bit about the history of this series. It was started back in the mid-60s, like so many others. But the X-Men never really made it, the sales couldn't compare to the Fantastic Four and all the others. So their story ended in 1970: the series was discontinued. No more stories of Professor Xavier, Cyclops, Marvel Girl, Angel, Beast and Iceman. Gone the threat of Magneto, the Juggernaut and the Sentinels.