By which I mean is still funny, and has a minimal amount of jokes which aged poorly (not stuff that aged poorly from stuff they couldn't have known about, such as a joke about someone dying in a certain way, but then someone later died in a similar way, but aged poorly due to how problematic they are).
Dr. Strangelove
The Big Lebowski?
It's a little less than 15 years old, but Burn After Reading has aged exceptionally well given the recent ineptitude of the :cia: