I'm not disagreeing with you both and I know what you mean. I just have different approach. Alien as a monster in the first movie is just a metaphor of something unworldly or simply ... alien to us humans. Movie
Alien doesn't really care how we call it (an alien, thing or whatever) because it's not important.
Aliens unfortunately changed that. Paying huge attention to those names kills the spirit of it. To be honest, all those names, Xenomorph, Protomorph, Deacon, Neomorph are silly. Couldn't care less
Predator is not part of the franchise