Ed here: On the A.V. Club there's a discussion about actors who are either a) always the same no matter what role they're playing and/or b) so distracting that their mere appearance takes you out of the movie. The most interesting comment came from a woman named Tasha Robinson. I think she articulates the problem very well. for the full discussion go here:
"I recently pitched an Inventory on once-talented-and-diverse actors who have fallen into a rut and just play the same character over and over, essentially serving as parodies of themselves. Keith said “What, you mean ‘movie stars’?” Oh. Yeah. Right. I guess that is a lot more common than I thought. After a certain point, I tend to find really big stars distracting in a film because of the likelihood that they’ll just be going through the motions of the familiar role that made them famous. Much as I love Samuel L. Jackson’s charisma, I’m with you on him as someone who can no longer disappear into a role. (Which for anyone who saw him in Spike Lee’s Jungle Fever is a serious pity.) I also get this from Tom Cruise, Bruce Willis, George Clooney, Al Pacino, and Keanu Reeves, who all these days either feel like themselves in roles or themselves shouting “Look at me putting on a mask!” But the two actors who most throw me out of movies are Jim Carrey and Robin Williams. In their comic roles, they’re both so mannered and routine-bound and artificial that they tend to throw off even the most mannered, artificial movie. (A Series Of Unfortunate Events, for instance.) I recently re-watched The Truman Show, and I felt more than ever that it’s a really good film that could have been a masterpiece, if not for Jim Carrey doing the exact same gestures and grimaces and squinting and flailing he does in all his other comic roles. "