I kinda like Motherofgod's
suggestion because I too have had the same experience when genre browsing.
The Hangover genres include: Comedy | Crime | Mystery | Thriller. Two more than mentioned on IMDB (which shows only "Comedy | Crime")
Albeit the movie is in a thriller like pace and there is mystery, I think it's safe to say that most people who watched it wanted to because of its humor. It's main genre would be Comedy. If I saw the words "Crime | Mystery | Thriller", the Hangover would not be the 1st movie that would come to mind, but rather a suspenseful murder action film. Shaun of the dead is listed as Comedy | Horror in both our listings and IMDB, which seems appropriate (although there is a lot of zombie killing action
On the other hand, the process of renaming ten's of thousands of movies just to simplify genre browsing would be a logistical nightmare, and perhaps would require more time and energy than would be saved. The Hangover is the highest hit movie with 400K, maybe we can compromise and only adjust the movies with higher hits, or on a per report basis?