You guys are right on a lot of these, but it also feels like a tad bit of criticism.
A lot of these nikkas have such a unique personality in real life that you hire them for the purpose of exuding that on-screen.
You don't put Christopher Walken in your film to act like somebody else. Jack Nicholson is one of the greatest actors ever and he's essentially "Jack" in every movie.
Hollywood was built on that premise. Just look a Bogart and dem.
I personally think De Niro is the GOAT because he's just as good subtle as he is intense.