Rebecca Romijn played a non-comic character role in the Punisher.
Ryan Reynolds played a nobody in Blade. Yeah, who really knows much on Blade before seeing the movie, even less with Hannibal (Lecter?).
Jon Favreau played an almost mute character in Iron Man. And starred in a movie that Marvel might want to forget in Daredevil.
Halle Berry is in Catwoman. Nuff said.
Actually there'd be no problem if Eckhart lands on a Marvel job. When he starred as a disfigured villain in DC Comics, now there lies the problem to land a starring role in Marvel comics. I'm not saying he's "banned" from supporting role, but Steve Rogers or Hal Jordan can't be seen as the Two Face.