> The experiment isn't entirely meaningful, because it is culturally dependent -- not just the star-ness, but the expectations of the performance. You don't have to go back very far in time to watch actors who were highly praised but seem off now. And go 20 years in the future, and a lot of what you see now will seem weird and fake.
Exactly that. I was just watching King Kong the other day, and most of the acting reads as terrible today. Delivery's bad, physical acting's way too much, timing's extremely bad. Ed Wood level, much of the time, and that's not an exaggeration. Some of the best (to my modern-viewer perceptions) is from the side characters. Yet, presumably, the leads were at least considered OK actors, at the time. This is true for lots of older films, especially before the 70s or so when the typical style seemed to shift to something much closer to what's in use today, and requires adjusting expectations and some, if you will, immersion therapy, to get over that hurdle and start to enjoy them on their own terms.
But then again, you can go back all the way to the silent film era and find some performances that still feel real and very good, even today and without much expectation-adjusting. Some of it seems to depend on the country producing the film—so, again, it's about culture. And comedy seems nearly immune to the problem, I guess because actors in comedies in all eras are rarely even trying for "believable", and are always kind of in on the whole thing with the audience.
You also see this with oration. Old speeches that are recorded sound totally strange. Part of it's that we had entire accents and styles of speech that were once common, that are now all but gone, a century or less later. Makes one wonder exactly how alien the past might have been, really, if one went even farther back. Written language makes it seem so close, at times. And yet....