Not exactly a Bible topic, but who knows.
I am a sci-fi fan. Stargate, for example.
Lets say that some civilization will develop to such a state of science and technology that they will apear mighty as gods in the sight of less developed civilization. Nanotechnology, destroying/creating planets, stars, maybe some kind of body-less evolution etc., you name it.
How to recognize they are not the real God, with certainty?
Answer = The same way we find out if "our" current religion is right, or just man-made... You seek God until he makes the truth clear. It's not about studying the alien, the technology, or the religious teaching... it's about finding the truth about GOD.
If we don't seek God until we find him...(If we're willing to just follow what makes sense to us and/or our limited understanding of the scriptures)...then we're already set up to be deceived.
If you think you can have a correct religion without having a living, speaking, active God...then you've joined a cult. A cult used to be defined roughly as "a set of religious beliefs without the deity to back it up" (regardless of the charisma of the leader). It's about whether GOD is in the church, not the attributes of the leader...or whether the preaching sounds good...it's about GOD. That's why I say if we have doctrines, but God doesn't do stuff, we've got it wrong. We've got to take it to God until HE shows up.
BTW, that's exactly how prophecy worked in the OT, and exactly what the disciples had to do until the day of Pentecost. They had to seek God until he showed up. None of this "I think this is what he means"...they had to seek him until he spoke.... and none of this "I think this is what the comforter is"... it was seek until he showed up.
With love in Jesus,
Kelby