Of course it’s all subjective. It’s art, not science or industry or whatever.
Consensus is as close as you’ll get to objectivity.
Acting, to me, is first and foremost about emotion - conveying emotion, and evoking emotion. Conveying emotion means convincing viewers that the character is feeling an emotion that serves the story. Evoking an emotion is making viewers experience a required emotional reaction, be it sadness, happiness, fear, joy or whatever. Being able to covey or evoke emotion is far more important to an actor than, say, being able to fake an accent.
What part of Noh don’t you understand? 
As an aside: I wonder if there’s a massive temptation for, say, a Hollywood actor who just got their big break in the #1 movie in the country to — well, play up the reverse of whatever they did when then making the rounds on talk shows and the rest.
Like, if America suddenly falls in love with you as a gruff cop who’s never at a loss for words, and you pretty much are kind of gruff and pretty quick with a fitting remark, would you try to present yourself as, say, calm and upbeat while stammering a bit, in hopes of impressing everyone with just how great a Capital-A ACTOR you are?
It’s a fascinating question. There are so many elements to an actor’s performance that your judgment of an actor may be based on only one element.
For instance, if you are someone to whom the accent is important, then you may have a very high opinion of Meryl Streep or Hugh Laurie, and a corresponding low opinion of William Hurt or Joseph Cotton. (I’m thinking very specifically of “Gorky Park”, where one could hear the Russian accent coming and going throughout the film, or the Boyer/Bergman/Cotton “Gaslight”, where Joseph Cotton was a British police detective with an American accent.)
How important is an accent to you, as the viewer/listener? In the example above, I was bothered by Joseph Cotton for about fifteen seconds, and then, the rest of his acting made me not notice the accent at all.
It’s often a huge revelation about someone’s acting skills when you see them live, and they’re playing multiple parts in the same show. Watch a ‘Twelfth Night’ where Antonio and Malvolio are played by the same actor - do you see the two characters as being different, or are you distracted because the actor has not succeeded in establishing the difference?
It’s also interesting to watch a film or a performance with a range of actors - I’m thinking of the film of ‘Midsummer Night’s Dream’ from the mid-nineties, where Stanley Tucci was outstanding as Puck, and Kevin Kline was fantastic as Bottom. And in the other corner, we had Callista Flockhart as Helena, and Michelle Pfeiffer as Titania. You may have a different opinion from mine, but I was not convinced they even fully understood the words they were saying, let alone inhabited a character in a convincing manner.
How much do you value versatility over the course of a career? I’m thinking here of Keanu Reeves - there is no one I can think of who could possibly have been as good or better in “Bill and Ted”, “Speed”, and “John Wick”, but I did not enjoy his Shakespeare at all. (“Much Ado about Nothing”, where he played the most truncated Prince John ever in a film where Denzel Washington and Michael Keaton shone in their roles. I never did see his ‘Hamlet’ for Manitoba Theatre Centre - I’m told he was a wonderful colleague, but he was not a very convincing Hamlet.)
Sometimes, two versions of the same film, or same story, may help you see the difference between good actors and less skilled actors. I’m thinking here of ‘Truly, Madly, Deeply’ with Juliet Stephenson and Alan Rickman vs. ‘Ghost’ with Demi Moore and Patrick Swayze - the scene where Juliet Stephenson is in the therapist’s office having the ugliest cry imaginable is heart-breaking; Demi Moore looks like her tears came from an eye dropper and cascade down her pretty, made-up face. I know which of the two I found convincing! (And the character actor who played the subway ghost in ‘Ghost’ should have got an Oscar for that 5 minute scene!!)
It’s a huge difference between film and stage as well - in both cases, the actor may well be trying to portray something that is not reflected in reality. Think of those Christmas films shot in June/July, where there’s fake snow all over the ground, the actors are in heavy coats like it’s winter, and yet, it’s 30 degrees out and everybody’s sweating! Or in the theatre, where I only have to turn my head away from the stage to be reminded of where I really am, and yet, the person onstage has completely convinced me that we are in a factory, or the sewers of Paris, or a bridge over the Seine. But the film actor only has to sustain the scene until the director yells ‘Cut!’, and they have as many takes as the light will allow - the stage actor has to sustain their part(s) for as long as the show lasts. And some of the smallest roles onstage can be some of the hardest!
Anyway, my two cents worth…
Which average? The average of all people who have “actor” as their job title? The average of all people who are trying to have actor as their job title? The average of all who have been credited in TV shows, or in movies? Those who have received top billing? The “average movie actor” is probably someone that nobody’s ever heard of, because there are a lot more minor roles in a movie than major roles.
It doesn’t matter because a slightly better than average actor is not what people consider a good actor.
You can’t objectively rank acting without making subjective decisions about how you are reducing something complex into a single number. It’s nonsense basically.
Bear in mind that acting never takes place in a vacuum. Even if Moore could ugly-cry, there’s no way that the studio would have allowed their star to be any less than beautiful for even a minute.
America’s next great reality show?
Look no further than the World Acting Championships!
I think now would be the perfect moment for a dramatic…
PAUSE!!!
Some skills of an “actor” could probably be objectively measured with some sort of double-blind “would the real (foo) please stand up” test, in which people attempt to fool strangers into thinking they really are (some character). Not quite sure how you would actually go about setting such a test up, but it could measure the “disappearing into the role” aspect of acting.
That said, that’s by no means the sole job of a performer. I mean, when I watch Erin Brokovich I don’t know or care if Julia Roberts is 100% convincing as the real Erin Brokovich, because (a) I’ve never met her, so how would I know? and (b) if I just wanted to watch a 100% real life depiction of a person, I’d watch a documentary about them. So presumably the skill of being an Actor is not in 100% perfect mimicry, but in striking a balance between that mimicry and being entertaining, showing emotions in a way that is more-than-real life but not intrusive, etc.
Perhaps you could affect a limp or put a small bowler hat up the back of your jacket because the Oscars love a heroic disability and you never know when the Royal Shakespeare Company might be watching.
This thread prompted me to re-read Michael Green’s Art of Coarse Acting, which is now on audio-book. Its very much taken from the non-good actor’s perspective of how you can draw attention onstage in even the smallest non-speaking walk-on part. Well worth finding if you or a loved one ever toyed with am dram.
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The ability to convincingly portray a real person whom the audience already knows is impressive but probably overrated. I’m not sure it’s any harder or more important than the ability to create a compelling character who’s never been seen before.
As an aside, IIRC when Bruce Greenwood got cast as President Kennedy, he figured that he could mimic the super-recognizable way the guy in fact talked in public, which is what impressionists of course exaggeratedly riff on; or he could do an eerily accurate version of the way Kennedy spoke when he was just talking things over with his brother and the Secretary of Defense and so on, which is what the character pretty much spends the movie doing…
…and, he soon realized, the problem is, if you do the latter perfectly, then audiences think, well, that sort of sounds like JFK; he’s not as good at it as my uncle is, or even as good as that fat guy I went to high school with; but, yeah, it could’ve been worse, I guess.
In the 30 Rock episode Jack-tor, the character played by Alec Baldwin,Jack Donaghy, is supposed to act in a skit. One of Jack’s challenges is what to do with his arms.
As soon as I notice the actor’s arms (not the character’s, the actor’s), it takes me out of the scene.
I can think of two broad criteria, which have at least an element of objectivity, by which good acting can be evaluated.
The first is realism: how closely does the actor look, sound, and behave the way an actual person in that situation would in real life?
The second, which can sometimes be at odds with the first, is effectiveness: how well does the actor’s performance have the effect on the audience that it is supposed to have?
Some examples:
A stage actor needs to speak loudly and clearly enough so that the audience can hear and understand what they are saying (even if a real person wouldn’t be projecting to the back row in that situation). And they’re often expected to “cheat out” so the audience can see their face, even though it might be more realistic for them to directly face the person they’re speaking to.
An actor sometimes has to “wear their emotions on their sleeve” more than a real person would. The actor has to let the audience know what their character is feeling by the way they speak and their facial expressions and body language.
If the point of a line or action is to get the audience to have some particular reaction, such as to laugh, then a good actor may say or do it in such a way as to maximize that reaction, which might be realistic or it might be wildly exxaggerated and artificial, depending on the type of show/movie.
Agreed; the example you cite, about a stage actor, demonstrates a difference in the art between the two forms.
I also suspect that, over time, the expectation that (at least in dramatic films) “realism” is valued in film acting has changed. Older films, by comparison, often seem to me to be more over-the-top in the acting style, and may come across as “bad acting” by modern standards, but it may well have been that that style was the norm decades ago.