This would be reinforced by the fact that invariably, the Humans team up with the technologically superior (but warlike) alien race, to defeat the bestial, technologically inferior alien race. Perhaps the supposition is that while we lack the technology and ritual of the higher alien power, they can learn from our cultural mores that arent ENTIRELY based on violence, religion and war.
Then again, the humans in Starcraft are pretty treacherous and back-stabby, while the Protoss are almost universally portrayed as good guys. Generally, it seems that the humans are flawed, but ultimately the good guys, while the zerg/flood/aliens are universally evil. The protoss/predators/covenant are warlike and zealous, but tend to learn and cooperate in the end.
Of course, there are plenty of sci-fi franchises that use a dichotomy, or entirely other system of hierarchies, but this particular system has led to some of the more successful franchises. I wonder if anyone knows of any credit being given by the makers of halo and/or starcraft to the producers of alien and the predator movies…whether consciously or not, they were almost certainly influenced
