Nobody outside of comics really knew of Deadpool or Guardians of the Galaxy before they became movies, and look how well they turned out. Likewise with Jessica Jones, Luke Cage and Iron Fist. Okay not so much with the last one but you get the idea.
Again just because a character is well known doesn't mean their movie will be any good, just look at the trainwrecks that are Spider-Man 3 and Batman v Superman.