Re: wat if they built up to x men, like avengers?
I don't think it would work that well for the X-Men, even if they get huge actors to play the lead roles.
For the 1st X-Men movie, people would expect the most well known faces of the X-Men, not 4 to 6 lead-in films featuring the origin story of Cyclops, Wolverine, Jean, Storm, Prof X and Magneto.
The prequel films for Wolverine and Prof X/Magneto didn't do so bad at the box-office because they were already introduced/developed in the earlier X-Men films and the general audience are already familiar with them. But imagine if they released those films first before a X-Men film featuring all the familiar faces, they would probably earned less money at the box-office.
Me. I Am Psylockolussus... The Elusive Mutant.