Monty Python's Holy Grail and Life of Brian were absolutely genius. Meaning of Life was good, although it seemed a bit forced at times.
The Holy SNL Trilogy of Caddyshack, Animal House and Fletch are obviously excellent.
I liked most of Appatow's movies, but Amy Heckerling (Fast Times at Ridgemont High, Clueless) is better.
This is Spinal Tap and Best in Show are both excellent.
Office Space is genius
Airplane! and Airplane 2 both age very well. I know the writing team was completely different for the two movies, but I liked them both.
I like Blues Brothers, but I don't know if it is because of the comedy, the music or it just kind of works as a movie.
The Jerk is pretty good, although I don't know if I consider it an all-time great like some do.
The Hangover I and the Hangover III. II wasn't bad, but it was basically the same as I.
Not Funny:
The 80's sex comedies like Porkys and Revenge of the Nerds are not remotely funny, and kind of offensive in hindsight.
Farley and Sandler's movies didn't age well. They were amusing in the 90's, but seem idiotic today.