If you want a villain PC to play against the other PCs, I think Chancellor Palpatine or Lex Luthor could work.  Magneto could also work as someone to divide the PCs up, but only if the people of this world don't accept "fictional" beings. 

In fact, I could play as Lex Luthor instead of Tony Stark, and just have him start building power in New York to try and take over.