Originally Posted by def28
Magneto and Prof X were always built up from X1. The intro to X1 and FC is identical.
Yes, many origins are hinted at, and then they are expanded upon in further films when the characters get to take their turn in the spotlight. We got 3 movies where the team-members were in the spotlight, only by the 5th did we get one focusing on the team leaders, so of course, people would have been upset if that had been the first x-men movie, as generally the books are about the team members first and foremost.