I'm really not discussing the absolute value of old movies vs. new ones, I'm definitely not expert enough on the subject. I was rather trying to point out other kind of effects I thought played a role in explaining the pattern pointed out in the OP. I used the parallel of music because I thought some of these effects were relevant in both cases.
IMDB top 250 list is dominated by old movies, which conflicts with my perception (shared by majority of people as far as I can tell) that new movies are far better than old movies (comparing either top with top or average with average).
I have a simple theory why IMDB is wrong: