Let me set a scene.
It's the final level of Crysis. I'm battling my way through flooded chambers on my return journey from the reactor core. As I happily blast away with my shotgun at the small flying aliens a random thought pops into my head, “If the aliens predate humanity by roughly two million years on earth, are they actually aliens?”
This got me pondering. Obviously they are alien in the sense that they are not of earthly descent, however they are less 'alien' to earth, for example, than humans having inhabited earth two million years prior to humanity. Furthermore the legal definition of an alien is, 'a person who is not a citizen of the country.' Surely having some form of civilisation on the island (and suggested elsewhere) counts as settlement? Logically the aliens could not be more alien to that area than Europeans are to Australia, Yet as Australians we don't call ourselves alien to the land, having settled the land we are not originally from. Certainly they are extraterrestrial, but following this logic are they actually aliens?
I think it's an interesting question and one I'd like to hear other opinions on.