Perhaps alien "people" haven't fallen - in the theological sense - so don't need a saviour? Are aliens sinless quite naturally?
But if they have "fallen" then it seems unfair that only humans get the Son of God on a short visit and aliens are left to stew in their own juices. What does it mean to be "fallen"? Not following the supposed commands of a murderous, middle eastern tyrant? This is just more slave culture exegesis for the jewish-christian-muslim slaves of yhvh-jesu-allah. We don't need no stinkun theocratic regents claiming sovereignty over the whole universe for their imaginary despots. Nuke those sand-lands into glowing glass. Maybe it would make for good roller skating.