I love the gems of classical cinema but I have never seen a great TV show from the past. Either I am ignorant or they are simply pouring more money and creative juices into TV nowadays.
Really? You don't think there are any great TV shows from the past?
If we just want to stick to the science fiction genre, I would submit Twilight Zone
as one example. Frankly, I'd also offer TOS. For all it's cheesy 60's goodness, there's a lot of real high-quality storytelling in there.
Also Mission: Impossible.