I think for me, when I say that someone is a good actor, it is because they can make me care about the character that they are playing. They can make me believe in them as a person. There are plenty of actors out there that I enjoy watching but they dont make me care about their characters, they just make an enjoyable story. Actors like John Wayne, Stephen Graham and Brad Pitt make watchable and enjoyable films but they dont make me care about them. Christopher Eccleston is an actor that does so does Denzel Washington.