Watching actors as a super recognizer...
I am a super recognizer, which means I can very easily recognize faces, even if time or something else changes them a bit (gaining or losing weight, different hairstyles, wigs, beards, coloured contact lens, wearing sun glasses, aging or something else).
For me, it's also a joy to watch actors and actresses doing their thing and recognizing them in each role, their facial expressions. Every one of them has their own style, and if I watch somebody in several different roles, I also recognize several facial expressions which are unique to them, because every face and it's movements are unique.
An example I have for this is Tom Hiddleston, I have watched almost all of his films and shows and two few theatre plays for ca. 14 years now. For instance, he has a unique way of raising his eyebrows in specific situations when he is acting and he can also portray moments of vulnerability very well, with micro expressions of his eyes.
A different actor would of course look completely different in the same scene and their micro facial expressions would look quite different. And of course, this also depends to some extend of the choices of the director.