We often see lists of "best 100 films of all times" or "best 100 albums", but I only saw a list of best TV series once or twice. I tried to think about reasons for this, and the only explanation I could think of was the TV series are very related to the time when they are made, and an excellent TV series made 20 years ago wouldn't be very interesting to us now.
What do you think about this notion? Can you suggest other explanations?