Broken Tusk remarks that Aliens are only good for training newbies on. They're tough and fierce but they're not smart and they don't have weapons.
What I think every bit of media has completely missed is that what would make the Alien an exciting challenge for the Predator is that the Alien is a better hunter. Like sure the Predator can just shoot it -- but the Alien is doing as good, if not better, a job of hunting it as it's doing of hunting the Alien.
That's the real challenge. Predators aren't here for a massacre, they're here to hunt.