I vote Vegas. I love the first one, but Vegas Vacation just cracks me up every time and... makes me want to go to Vegas again. I think this one is an all time classic. Cousin Eddie's trailer on nuke test land, Wayne Newton hitton on Bevery D'angelo "this is Shanendoah, it's my home" (always busts me up), the misadventures of the kids, all of it.
Probably set this up at the wrong time, being just after Christmas, but oh well.
"Eddie, has anyone ever told you you're bad luck?"
Cousin eddie, Busch can in hand, "you know Clark, those were my mother's dying words, but..."