Some very interesting views here. I agree with some of them but can’t agree with the comments about Judi Dench and Nicolas Cage.
I don't think Judi Dench plays herself in every role, you only have to watch Philomena in which she plays an Irish woman who is trying to find the son she was forced to give up for adoption and Red Joan in which she plays a retired widow who is suddenly arrested and interrogated by the Secret Service, there are many more examples of very different roles she has played.
Nicolas Cage has played some very diverse roles and received numerous awards and nominations, not only the Oscars but Bafta and many other respected bodies such as The Screen Actors Guild. He’s not dreary either, look at Raising Arizona, Face Off, Peggy Sue Got Married, Matchstick Men and The Weather Man, all very entertaining films. His dramatic roles include Leaving Las Vegas for which he won an Academy Award and Captain Corelli’s Mandolin.
I disagree with other suggestions such as Tom Hanks, Julie Walters and Nicole Kidman too but it’s always good to read opposing views.