Predators all the way!!!
The predators are tough, well-equipped, and are strategic. After killing most of the survivors, they should scare the shit out of the last ones alive, making it easier for them, and harder for the us. Predators can only be defeated by the last survivor because they want to make it a happy ending. Only a squad of well-trained people can defeat a Predator, if the predator was stupid enough to show up in front of them. Only the aliens can kill them, but still requires a lot of aliens to do that. When they die, their comrades honor the other species, except if it is an alien. All this making the Predators the high-class species of the three.