This is in no particular order.
1. Ian Mcshane
2. Daniel Day lewis
3. Johnny Depp
What say you Getbig?
They are all outstanding. McShane's Al Swearengen was one of THE best characters on television, ever.
I used to not think all that much of Depp, but his performance in "Public Enemies" ... for my money, his John Dillinger was one of THE coolest motherfuckers ever seen onscreen. The way in which he seduced Marion Cotillard's character was a particularly good monologue. Even the actress had to be wet after that scene
But there's truly no way to score a top three actors of all time. You've got Brandon, Nicholson (even though he is usually just "Jack"), Patrick Stewart -- heck, even Brian Cranston has stood up as a truly epic actor.
Best actresses would be a harder thing for me to nail down because I'm straight and I have a hard time separating good looks and acting ability. But I can say that gorgeous South African chick -- err ... damn. What's her name? AH! Cherlize Theron! -- is a fine, fine actress. For comedies, I honestly think Jenny Aniston kicks ass (and yes, again, I'm biased since I've had a crush on her since "Leprechaun"
). Watch "The Break-Up" and tell me she isn't funny as hell in that -- Vince Vaughn too, for that matter.
As I said, there are really too many actors and too many different genres to pick a top three with which a majority of moviephiles might agree upon. Bruce Willis is great, Morgan Freeman is amazing, Denzel Washington is the man, etc., etc. James Earl Jones, Martin "Cpt. Williard" Sheen, Powers Booth ... we'd have better luck hunting snipe than agreeing on the best actors and actresses, methinks