Vanderbeek, Slater, Campbell make sense to me. They still pop up now and then but they are not nearly as busy as they once were. You can also make an argument for Kevin Bacon. You could even make an argument for Chris Tucker but he's never really been a busy actor.

Hunt, Stone, Moore, Davis are on a different level. They are still working but they went from being at the top of the game to supporting players in bad films.

But greg kinnear has been all over the place, the same with Billy Bob Thornton (now, if you want to wonder what happened to Billy Bob the serious actor, you might have something.)John Leguizamo has been as busy in 2000 as he was in the '90's. Tim Roth doesn't get as many leading roles but he's hardly disappeared and is still a very busy actor. Most of Love Hewitt's film roles were in 2000's and she's back on TV. She's not in the tabloids as much but acting wise she's as busy as she was in the 90's. Chazz Palminteri was never really a leading man and is still working steadily. And then you named Ryan Phillipe who's most acclaimed work has been in this decade and he just had big roles in Breach, Crash, and Flags of our Fathers.