Not every television series from the 1960's holds up by modern standards. I'd argue that most don't. So it takes a certain type of show, a certain style for something to be relevant over 50 years after it's initial release. It usually helps if the show has an element of science fiction to it (like this or Star Trek). The plots of these shows deal with eternal philosophical questions that will always be relevant even if the techniques and technology used to create them are not.
The Prisoner falls in the camp of relevancy because of the vision of McGoohan. As the main actor, producer, and often director, his singular vision of what this show was to be practically forced this show to stand out above the crowd of mediocre 60's spy and action dramas. Instead of focusing on standard spy plots, McGoohan created a show that focused on the metaphysical, the concept of individuality, the role of government. This isn't a show about a spy locked up on an island for what he knows, that is just the setting. This is about an individual's struggle to reject conforming to society and the issues that this creates. The setting is pretty, the characters unique, the direction often breathtaking, but it is the concept that keeps this cult classic in the hearts and minds of viewers decades after many other shows have been forgotten.
The Prisoner falls in the camp of relevancy because of the vision of McGoohan. As the main actor, producer, and often director, his singular vision of what this show was to be practically forced this show to stand out above the crowd of mediocre 60's spy and action dramas. Instead of focusing on standard spy plots, McGoohan created a show that focused on the metaphysical, the concept of individuality, the role of government. This isn't a show about a spy locked up on an island for what he knows, that is just the setting. This is about an individual's struggle to reject conforming to society and the issues that this creates. The setting is pretty, the characters unique, the direction often breathtaking, but it is the concept that keeps this cult classic in the hearts and minds of viewers decades after many other shows have been forgotten.