A "major classic" would be a video that the majority of people that watch such thing know about and consider good. Classic literature would be books written a long time ago that are still read today and considered worthwhile to read. A "minor classic" would be one that a small, but significant group of people know and still watch, or one that large people know about, but do not consider of primary importance.

classic = work of art that is popular for a very long time, often hundreds of years after the composer's death. a major classic = a well known classic a minor classic = a lesser known classic