Who are the best actor and actress ever?

Why is everyone so hot on male actors and nobody's mentioning women! I've only seen Sigourney Weaver and Julia Roberts mentioned (by anyone other then me) and they're both mediocre in my opinion. As before what about Maggie Smith, Julie Walters, Vivien Leigh (in A Streetcar Named Desire she was fantastic), Juliet Stephenson, Emma Thompson?
I don't see why Keira Knightly gets a mention on the list. She just pouts her way through every role.

Can't believe Al Pacino isn't on list!! What bout Johnny depp, Sean Penn and Matt Dillon all great actors!

for sheer versatility Gary Oldman has got to be up there. The man is a chameleon. He played a myriad of real-life characters who couldn't be further apart from one another with exceptional quality (Beethoven, Lee Harvey Oswald, Sid Vicious!!!) and he rivals even De Niro in the violent nutcase stakes (State of Grace, Leon, True Romance). He can also play understated comedy (Nobody's Baby) and ham it up big-style and still look cool (Dracula). One of my favourite performances of Oldman's is that of Rosencrantz in Tom Stoppard's brilliant 'Rosencrantz and Guildernstern are Dead', which is a very novel take on Hamlet. The man is a genius.

Obviously all great actors on this list and a whole lot more are not on it!

I must say that Daniel Day-Lewis has probably impressed me the most over the last fifteen years or so, along with Russell Crowe.

Edward Norton and Christian Bale are also modern favourites.

But in terms of acting in so many great memorable movies over a long period of time, perhaps the award should go to Robert DeNiro?

Robert De Niro is undoubtedly brilliant and playing violent nutcases, but because he's so good at it thats all he ever plays these days. I think the test of an actor/actress is their versatility and they need to play a broad range of characters to display that.