Well if it's leading into the original film, and our first encounter with the original creature, or at least the creature responsible for all the eggs and the happenings on lv-426, then why not
"The Alien"
Unless they go with something like Alien: Inception. Just "Alien" has already been done. The predator is doing the same thing now anyway. If terminator had not done genisys, then we might have Alien: Genisis. I wouldn't rule out Exodus though. Especially given the current situations of the engineers and colonists.