You know, some of the reactions to this amaze me. Affleck's career missteps have been well-documented but he's also put out some stellar stuff (and not just as a writer/director; if he was such a terrible actor, The Town and Argo wouldn't have been good movies since, ya know, he played the lead). Meanwhile, I've seen people on this board championing guys like Karl Urban, who has been good in some things but awful in others (Chronicles of Riddick, Doom, Priest). And while you can argue that those were simply bad movies, I say this to you: Would Daredevil or Gigli been good films if they starred a different lead actor?
The answer is no.