Imdb is a surprising source of hilarity in many user reviews.

Such as a film called Wolfman (or something similar) where the reviewer wrote “Eschewing lesser directors such as Spielberg our director opts to show the monster the monster in the first 2 minutes with a masterful shaky handy-cam technique”.

Or the modern War of the Worlds movie where someone noted the aliens “have been destroying the Earth with UNBELIEVABLE FEROCITY and then suddenly they send down a Wormy Proboscis into the basement in which the heroes are hiding which goes “Ooohh Look a mirror!”

A little harsh perhaps but very funny.

Prometheus user reviews are worth plenty of study, but one of the best ones was “why are the Progenitor aliens messing about with bio-weapons that clearly they cannot control?”

(In the movie the large Progenitor Aliens are often shown on old video reels running in terror from something they have been developing).

Or the "Battleship" reviewer who said "As a huge space alien that someone has fired a cruise missile at. Do you:

A. Move out of the Way

B. Sink below the waves or

C. Hop straight into it like a giant frog"
(Battleship is of course entirely redeemed by using AC/DCs "ThunderStruck" and some Veterans!)

Or the Trivia for the 80's Howard the Duck Movie:

"On the DVD commentary for the film, one of the commentators claims that George Lucas reassured him that the project would, in 20 years, be seen as a masterpiece. As of the year 2012, the film was still considered one of the worst ever made."