Like some other people mentioned before...I am not very fond of the ALIENS Xenomorphs in "modern" times...I feel they should stay and always belong in the future.
When you bring them into modern or even historical times I feel you "dilute" the creature somewhat by making it out to be like any other monster in horror movies like the Werewolf, Bigfoot, Dracula, Frankenstein, etc. And though the ALIEN has been seen along with them I feel it has always stood away from that crew because it was extremely different (breeding, "insect-like" social structure,etc.) and because of the time-gap.
I won't deny that the 4 ALIEN movies being set in the future have a definite impact on my feelings but I just feel it's awkward to see them in modern times.