This is underlined by he question of the original sin. Adam and Eve sinned, and that made life imperfect for us because we are their children (guilt by presumed blood relation). It required god to send JC to help us out, because we couldn't have done it (whatever "it" is, and pity those who lived before JC and didn't get "it") ourselves.
Those who lived before Jesus are covered by his ransom sacrifice.
Ever hear of the resurrection and reward promises?
Whatever it is they couldn't do, was refrain from sinning. Since the punishment for sin is death, then death could not be evaded. Jesus' death paid the price o death for all mankind leaving those willing to take advantage of it able to eventually gain eternal life. Not on their own merit-but because the penalty had been paid for them.
If ETs appear, the question is whether they were put "to the test", and whether they passed it or not. If they didn't, then they didn't need JC's sacrifice to straighten out their lives, or are they still waiting for "it"?
Jesus died as a man for the sons of Adam. That's why he took the human form. His death isn't applicable to other humans or creatures who are not of Adamic stock.
Or maybe they answer to their own god, who did things a totally different way. If so, where does omnipotence go?
There are people here on earth who answer to their own ideas of gods and omnipotence goes nowhere.
If they have no equivalent concept then do they really have soul (or whatever god added to us to make us special), or are they just animals, even if more intelligent/cultured/<name the attribute> than we are?
There are people right here on earth who differ in concepts and whom Christians still consider to have a soul and are considered humans and not animals.
If they passed their test, does that make them superior morally to us?
It would make them morally capable of doing God's will perfectly because they haven't suffered physical the consequences of sin. Would it make every individual in their group incapable of sin? No. Sin will continue to be a personal choice.
Do we take their word for it?
Mankind isn't that gullible. Especially since mankind has a tendency to deceive due to ulterior motives.
Do they have to bow to our god if they passed, or we to theirs? Are our gods miscible?
Why would a Christian feel he has to bow before a concept of God that comes across as totally alien? Did Christian missionaries begin bowing down to the God's of non-Christians
simply because they found concepts of other gods? One doesn't need an alien race to encounter that situation. It exists right here on earth right now and Christianity deals with it as it would deal with any such concept. By rejecting it.
sociological questions go on forever, and have the potential of doing great harm to the population that believes in them - for example, an inferiority complex growing into unfounded xenophobia.
Christians already believe in creatures superior to mankind both physically and intellectuially-angels-and they haven't developed and inferiority complex so far.
2 Peter 2:11
Whereas angels,
which are greater in power and might,....
Psalm 8:4-6
4What is man, that thou art mindful of him? and the son of man, that thou visitest him?
5For thou hast made him
a little lower than the angels,....
They simply consider them a sort of elderly big brothers whom God simply chose to make superior to us for his own good reasons. In fact, they are said to have witnessed the creation of the earth itself.
Job 38
4Where wast thou when I laid the foundations of the earth? declare, if thou hast understanding.
7When the morning stars sang together,
and all the sons of God shouted for joy?
Yet that is accepted as given with no resentment nor ineferiority complex. So why would an additional big brother make any difference? It would simply be viewed in the same light. From a correct Christian standpoint.