How good a film depends on how entertaining it is, because at the end of the day thats why people are watching. Sometime this "entertainment" can be in form of admiring its mechanics (editing, cinematography) or characters (writing, acting), or plot (writing, directing) or any combination, but all art is about eliciting some form of appreciation in the viewer, whether that is emotional or intellectual.
Actually, the last post on STIV being made in the 1980s is a good example of how what makes "good art" is entirely subjective, and very tied to historical context. What people considered "good" about films in the 1920 and 1930s is very different than the 1970s and 1980s, for example. If you were to show many typical films from the former to the latter, they might complain that the acting is over-the-top, the plots not realistic, the sets fake looking, no challenging messages, etc. And if you show a film from the 1980s to people today, some might have the same reaction. Do you really think that any of todays "masterpieces" will be looked at any differently from many people in 2050s?
Taste is subject to trends and fashion, it changes over time, and what people consider artistic, or noteworthy, or entertaining, or whatever is entirely temporal. Anything with expliciti sex and/or violence in it was considered "trash" until the 1970s, and even then it was rejected by many people for its moral ineptness and such. Ever since the 1970s, if there was no "hard" subject matter, a lot of people looked at it as fluff, and not very serious.
Art is subjective, and the trends in its appraisal change as much as the fashion styles on runways, because there essentially is no difference.
It's not a question of whether I would judge the film by the standard of now but a question of many people doing so.
The point is that you attempted to invalidate that films success by asserting it wouldn't be recieved as such today, the implication being that the film isn't really as good as its reputation holds. Which is a circular argument--it wasn't released today, it was released in the 80s and was very successful in the 1980s, and if it was made today it would be quite different.