a mediocre movie by today's standards has like a 95% on rotten tomatoes.
Curious what film you're thinking of.
For the record, I feel there are a great number of old films that are overrated. I have listed them in other threads and won't repeat a full list here but I've got particular disdain for the historical reputation of Lawrence of Arabia for example.
But I think that many of the old films that survive to current prominence have done so precisely because they were the very best of the era in which they were produced. Most of the crap is essentially entirely gone. I'd be willing to bet, for example, that the vast majority of users on this board (which is nominally selected by sports interest rather than film interest) have seen fewer than 50 films that were produced in the 1940s. That sounds like a lot, but as a functional matter it's the equivalent of seeing only the five best movies produced every year in the decade. Those top 50 films probably attract the most intense interest and what you're seeing when you look at old films are the cream of the crop. There was certainly a lot of crap back then too, but the 1943 equivalent of "Cloverfield" is of only the most niche interest at this point in time while Casablanca survives.
EDIT: I picked the number "50" for films from the 1940s somewhat arbitrarily, only to make a point regarding the math of the situation. I then got curious how many films from that era I personally had seen and counted up my netflix ratings. To hammer the point home, I don't even fit the criteria of having seen 50 films in the decade because I've seen, according to my netflix ratings, exactly 49 films from that span of time. This is despite the fact that I have a much greater than average interest in older films. Given that, I'd be curious if there are even more than one or two people on the board who could claim to have seen 50 movies from the era.
Also, in terms of why the classics are considered to be epic consider this list of films from the 1940s: Citizen Kane, Casablanca, It's a Wonderful Life, The Grapes of Wrath, The Maltese Falcon, A Tree Grows in Brooklyn, The Third Man, The Treasure of the Sierra Madre, The Big Sleep, Seargant York, Adam's Rib, The Philadelphia Story, His Girl Friday, The Great Dictator, Arsenic and Old Lace, The Bachelor and the Bobby-Soxer, Rebecca, and the Bells of St. Mary's.
What an absurd murderer's row. And I would say at least two of those (Casablanca and It's a Wonderful Life) have extraordinarily strong cases even on purely modern terms against your pick of the Shawshank Redemption.
