To answer your question, which I know you asked orthonorm and he probably has a completely different answer, older movies just haven't aged well.
I can only think of a handful examples that have stood the test of time and will continue to do so, but considering how much goes into movies these days...it's not really much of a surprise they are better.
OK yes when directors like Coppola contributed to the studios thwarting their creative control in order to make a financially successful film there will be a dip in quality but I am still not entirely convinced that dip makes older films better.
Of course you have your Transformers of the world that are completely vacuous, however the development of the moving picture has made things better on the whole.
Higher production values, creative and extensive usage of cinematography, classical music scores that don't sound dated (most old movie soundtracks are dreck), better acting (and really with all the people trying to compete for the limelight in Hollywood, maybe I am naive enough to believe the talented ones will rise to the top), etc etc.
Or maybe you believe Steven Spielberg in that movies are going to be a dead medium soon.
I once believed that interactive entertainment was going to largely displace movies, and maybe one day it will, but I am not sure I see it going away anytime soon.
I don't know I think a lot of the newer films that have been highly rated are crafted superbly well.
I just don't like when people get nostalgic about the past, as if there was some sort of golden age and miss what is right in front of them. It's OK to reminisce sometime but anytime I try to go back to something that in my head looks serene, perfect and beautiful it ends up not having the same effect as when I first watch it whoever I was when I viewed it.
It's kind of like the point orthonorm made about Buffy. It changed TV but if you were to watch it today, it just wouldn't have the same impact.
Now if you like the older films because it reminds you of a time when you liked things how they were...well that's unfair I think to judge newer films in that light.
I can't stand the gratitous violence and gore of recent movies like that ridiculous Tarantino film Django Unchained or the new Evil Dead reboot. Yes both films have much more real problems at heart (like it taking a white man to free the black slave, etc)but I can't help but think people mistake this superficiality violence as something intelligent, because it's not.
I like to be entertained and also satisfy the artsy/pretentious part of my brain too. I am a snob and someone that can be easily entertained...which I think is a good combo to have.