I've seen a couple over the years: Robin Hood, Twelve Chairs, Blazing Saddles, and most recently Spaceballs. I found them all funny, theoretically, but they rarely got an open laugh out of me. It seems like most of the time this is just because the comedic timing makes every joke or funny bit land very awkwardly, or with just a bit too much space to leave room for any subtlety or reward for the watcher.
I feel like I remember the few I saw as a kid being funnier at that time. Is it just because my brain has been attention-poisoned with the rapid fire wit of modern comedic television?
IDK but conventions definitely change over time, so what played well with one audience may not play as well with a newer different one.
On the flip side, I feel like modern comedic stuff never has the great frenetic pace of stuff like Airplane!
I do like that about Airplane! so maybe it's just a personal taste thing. I did mention in another comment though when it comes to non-comedy I much prefer older, slower movies.