Heroes and antiheroes in literature

Perhaps everyone has their favorite movie or novel characters, and now you probably can remember one of your favorite heroes and antiheroes like Thor and Loki, Batman and Joker, Harry Potter and Voldemort, Sherlock Holmes and Moriarty, Peter Pan and Captain Hook, but what makes them so appealing?
Why do we like heroes? It is a known fact that no one likes know-it-alls or these Marry-Sew characters: sugary misters Right and Perfect. There is a secret: every character that you may like has his flaws. A perfect hero has four things: treasure, aim, secret and… a flaw.