Honestly, Nicholas Cage. I know people like to make fun of him and even go as far as to praise him religiously in a mocking satirical sense, but I really thing he is a great actor. He is great at selling a number of roles, whether it is a psychotic murderer (followed by law abiding cop) in Face-Off, a dirty cop turned hero in Snake Eyes, or a cold hardened gun runner in Lord of War (my favorite performance of his). I have yet to see an actor get into character and sell it as well as Nicholas Cage has, even if he does sometimes have a questionable taste in scripts. I feel nobody seriously recognize how good and versatile of an actor he really is.
Lord of War is probably his best film. At least in the serious vein. I think a large part of this stems from his not acting like Nicholas Cage. The Rock is his best non-serious role. Still decent acting without any of the insane craziness he is known for now.
The Rock really has to be Michael Bay's best work. It has the perfect blend of action and plot. The action isn't so over the top and mind numbing, the way Bay got with his later films. He managed to achieve and optimum blend of serious and silly with a fantastic cast. Sean Connery plays his role brilliantly and his constant jabs at Cage's whining always make me laugh. "Your besht? Your besht!? Looshers alwaysh talk about their besht!"