I know, this has been done to death, but since Deathdrop said about more fights that requires more thinking to determine the winner, I thought I'll try thinking one myself.
Here's the case: it's a 1vs1 battle, but each one is a mix. The battlefield is set in a Nostromo type vessel.
The Xenomorph: It has the shape of the Drone in Alien, thereby allowing it to blend perfectly into the surrounding of the Nostromo. It also has perfect knowledge of the ins and outs of the ventilation systems. It also has the fighting prowess of an alpha Alien (ala Grid), allowing it to put up a better fight in meele.
The Predator: It has the cunning and deciet and the ability to instill fear of the original Predator. Yet it also has the wide arsenal that the Predator from Predator 2 has (combistick, dartgun, disc etc, all the weapons the one in Predator 2 has).
Who do you guys think would win?
"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."