I get what you are saying, but what I am saying is that IMO if you say something like this about a show or movie then it probably isn't an all-time great. The greatest pieces of art need to stand up over time. JMO but you can't say that Seinfeld is a great show if you can't sit down and watch it and find it funny still. I could watch stuff like Arrested Development over and over, same with Curb, so I say they are great. Seinfeld suffers a bit from the above, so it's knocked down my rankings a bit.
But you said great comedies shouldn't hold up, and I just can't get behind that. Caddyshack shouldn't be great if you only laughed at it with your buddies when you were drunk in college, but it's not funny now.