Ok, the pre-18 or pre-22 year old me would say:
#1 -- Star Wars / any of the first trilogy
#2 -- Blazing Saddles (if that is too politically incorrect, then make it Young Frankenstein)
#3 -- Animal House
Lots of other great movies mentioned, I'm trying to think of the ones that really shaped me & and I really loved, that may not have been mentioned already. I'll make another list for my post-22 year old me.