I happen to like Brad Pitt's acting but some say he is just too stupid. Don't know, but I did go to grad school with his college roommate and to no surprise they did quite a bit of partying and other unmentionables.
I think Saundra Bullock is about as bad as they come. Keaneua Reeve is so-so at best, definitely the one expression actor. DeNiro has kinda seeped into that as well although he is/has been a phenomenal actor.
Eddie Murphy's comic abilities have long gone down the tubes.