Haha, they're not that old. Movies were pretty much done with love before, actors weren't paid like today. And their budget wasn't 100,000,000$. Of 150 movies that are being filmed in 2011 and 2012 only 5-10 of them are "ok". And just check how many movies that became "cult movies" are filmed/made in 1990s and before. Many, but really many. Most of the good ol' directors and writers died, some of them are still active, but doing only low-budget movies. It's really sad to see that people underestimate older movies that are far more better than most of the 2010/2011 crap.
If you don't believe me, start downloading all movies from one older director/writer (Stanley Kubrick, William Wyler, Sergio Leone, Victor Fleming, Otto Preminger or older movies from James Cameron, Oliver Stone, Woody Allen, etc.) and see the difference yourself.