I just hate trying to pick top fives! If I must (in no particular order and subject to revision every time something else comes to mind):
Shaun of the Dead
South Park
Time Bandits
Life of Brian
..... Erm, you know - it's much easier to think of funny series than funny films. It's a simpler matter to sustain comedy for half an hour than for a full film. Some of the best there have to be Spaced, The Day Today and Brass Eye, Futurama, Red Dwarf, the Young Ones, Peep Show (I could go on for a while here). A preponderance of male writers, now that I think about it.