As the holidays approach, Clark Griswold (Chevy Chase) wants to have a perfect family Christmas, so he pesters his wife, Ellen (Beverly D'Angelo), and children, as he tries to make sure everything is in line, including the tree and house decorations. However, things go awry quickly. His hick cousin, Eddie (Randy Quaid), and his family show up unplanned and start living in their camper on the Griswold property. Even worse, Clark's employers renege on the holiday bonus he needs.

In the course of the three National Lampoon vacation movies, Clark Griswold has become an emblem for all that is sweetest and most ineffectual in the Hollywood husband. What he wishes for his family, most desperately, is that they have a good time. All he is able to deliver is chaos and hair-raising misadventures. 
Roger Ebert
RogerEbert.com

Sure, it's crude, episodic and half the jokes don't work, but 'Christmas Vacation' may be the only modern Christmas comedy which really stands up to repeat viewings.
Time Out Staff
Time Out