I suppose we all see different things in what we watch. Randolph Scott always plays Randolph Scott, same for John Wayne. They play the same character across different types of movies. I always though Robert Mitchum was good and Gregory Peck, depending on the role. But there are so many that were good in one role but stunk in another. Errol Flynn always played Errol Flynn. Someone like John Hurt can play different people and do it well. For all his weirdness, so can Johnny Depp if he wants to. Then you get the ones that are just miscast- Michael Keaton as Batman?!!! What?!! Just had a discussion with a friend up here, he adores Barbara Stanwick, who turns my stomach almost as fast as Bette Davis, Joan Crawford or Liz Taylor. It's like music- To each their own.
What do I know? I spend my evenings often watching old B+W movies. I'd say there are maybe 5% of movies made that are really good, the rest vary from decent to awful. About like life across the board in a way.