This is a topic I've always been interested in - why does comedy become dated, and why do some things date more than others?

As a kid i'd hear adults saying how funny Tommy Cooper was, but I have never found him even remotely funny, yet I found Harry Hill hilarious and Harry Hill's act seems to awe a fair bit to Tommy Cooper.
Nothing will ever be as funny to me as the first time I watched Monty Python's the Holy Grail - I was just the right age for it and me and my brothers were in absolute hysterics, as soon as it finished we rewound the video and watched it again, every bit as funny. At the time it was probably about 20 years old but seemed really fresh and new.
Similar story with Airplane.

I remember enjoying the sitcom "Game on" when I was in my teens - I went back and watched an episode a couple of years ago and it was completely awful, not funny at all and in fact a slightly depressing experience.