Brad Pitt is definately a good actor, or at least was up until he did Troy. Either the screenplay for that movie was horrid or he just had entirely too much coligen injected into his lips for him to speak properly... I enjoyed Troy for entertainment purposes, but it and Brad Pitt could have been so much more... Pitt did amazing work in 12 Monkeys, Fight Club, Interview with a Vampire, and even Snatch. I hope he doesn't turn into just a sex symbol / mindless actor.
Jim Carrey tops my list for this thread... Truman Show and Eternal Sunshine are two of my favorite movies, and Jim Carrey did an AMAZING job in both of them, especially Eternal Sunshine. I laughed at his comedy before, but didn't respect him in the least, now he is definately one of my favorite actors.
Leonardo DiCaprio is a tough one to place for me. He was amazing in Basketball Diaries and Whats Eating Gilbert Grape, then he was in Titanic and it went down hill for awhile. After he did Titanic he was turned into a teen idol / sex symbol and I lost a lot of respect for him for that. Since then, he was in one movie that I enjoyed a lot, Catch Me if You Can. I really don't know what to think of him anymore.