Leonardo DiCaprio. I can never believe he is the character I always see an actor trying to portrait a character. Like with other actores I can believe I am seeing something that happened. With DiCaprio I'm always aware that I'm watching an actor doing a performance.
I don't know if that makes a lot of sense. But it's one of the few "good" actor that makes me feel this way.
He did an incredible job in Django Unchained, but other than that I would agree with you. I don't believe it is his fault though, more a result of how he is always cast.