I prefer to think that they were created just like any other race, by Evolution. If the Xenos are artificially created, then what made the Preds? The reason that (how I see it) there was Xenomorph eggs inside a Space Jockey ship was IMO that the Jockeys were trying to use the Xenos as a Bio weapon and failed when the Xenos rebelled and attacked them, resulting in the crashed ship and the chestbursted Jockey.
"There are five possible operations for any army. If you can fight, fight; if you cannot fight, defend; if you cannot defend, flee; if you cannot flee, surrender; if you cannot surrender, die."