This one always bugged me (from mixael's link):
#3. One Planet, One Culture... Except Earth
Our intrepid space explorers make contact with a new planet named Generisis III (cool planets always have numbers) and make contact with the sentient species, the Latexx Foreheadians. Assuming peaceful contact is made, the heroes will be spending a lot of time learning about the Foreheadian culture, language, religion, and all other aspects of Foreheadian life.
But wait a minute. Earth has hundreds of languages, cultures and religions. There's not even a single culture which has "dominance," and the most common trade language (English) is barely spoken by half the planet. So why in sci-fi do we still have races who are "warlike" or "profiteers" that live on a "desert planet" or an "ice planet." Apparently all civilizations eventually just consolidate everything to avoid confusion?
Read more: 6 Sci-Fi Movie Conventions (That Need to Die) | Cracked.com http://www.cracked.com/article_17392_6-sci-fi-movie-conventions-that-need-to-die_p2.html#ixzz1ObPS5rg6
