I usually loathe those 'the book was better' whiners, but I will say that the Fletch character is WAY cooler in the books, and what you see in the movie is basically Chevy Chase being Chevy Chase. I enjoyed that movie well enough at the time, and we all quoted lines constantly for several months but I can't imagine I'd really be able to sit through it now. All the other guys in the movie are basically there for Chevy to bounce jokes and insults off of...
Vacation, on the other hand, I would think has many awesome lil things to keep you going thru the Chevy bits. Think about who all's in that thing: Randy Quaid, D'Angelo, Candy, Brian Doyle Murray, Jane Krakowski,
Imogene Coca etc etc.