+1
Difficult to say really, in the 1950's American films were rather bread without butter, and stale entertainment, (mostly because of G.I.'s returning home and wanting this kind of blandness, also the Studios incapable with logically competing with Television). Not to say there wasn't great films made in America during this decade, but to be blunt, were America failed, international cinema triumphed in this decade. My guess is the worst has to be the 2000's+, even before then it was getting pretty bad, but international and independent cinema, (and this is just my opinion), lacks a certain heart and soul, it's hard to place my finger on it. Perhaps its a measure of heavy-handed messages delivered without finesse, a pill that has no sugar coating. And Hollywood has entered an age of delivering no message without any finesse except for perhaps the occasional, (or bombastic), special effects. It just seems nothing really means anything anymore. That's not to say I'm not impressed every now and then, there are plenty of films from 80's onward that I have found to be wonderful films, it just seems they are harder to come by. Even in my favorite realm of avant-garde/experimental/underground, good original works seem harder and harder to find. But this is my take on the worst decade, so yes, 2000+.
As far as best decade, or decades, I would have to say The Silent Era, 40's, and 70's. Reasons being that The Silent Era ushered in techniques and film language which was revolutionary for their era. During that time, cinema's language was largely created within the first 20 years and not much has been changed or innovated to the extent that it was being created during those first few years. The 40's saw the creation of America's only film movement which was Film Noir, and the beginnings of the American avant-garde movement with film maker Maya Deren, in Italy there was Neo-Realism, but also, in America, the Studio system was creating amazing "story"-driven films that trump anything that had been made before, or really even since, it's time. The 70's saw the rise of "The New Hollywood", producing spectacular films constantly, but on an international level as well, the old New Wave masters were still making films and amazing the global cinematic community. On that level, the 70's was perhaps the best.
Now I'm getting a little long-winded, so I'll stop. But this is just my observations on cinema history.
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Imagine an eye unruled by man-made laws of perspective, an eye unprejudiced by compositional logic, an eye which does not respond to the name of everything but which must know each object encountered in life through an adventure of perception. How many colors are there in a field of grass to the crawling baby unaware of 'Green'?
-Stan Brakhage