The Goa'uld are a race of symbiotic aliens who traveled to Earth, as well as other inhabited planets, and took the inhabitants as hosts. Once on Earth, the aliens pretended to be gods in order for the inhabitants to worship them. The Goa'uld mainly pretended to be Egyptian gods, such as Ra, Horus, Osiris, etc.
This theory (though to a religious person is utter nonsense) is quite logical when you think about it. The universe is incredibly vast and old and the probability of intelligent non-human life somewhere out there is surprisingly high and....... Forget all that. This has nothing to do with this debate... This is just a question of are you open-minded or are you a rude ignorant bible-thumper. This theory may be false and it may be true but religious people will never give it a second (or even a first) thought because they are convinced that everything that is scripture is lies therefor this debate is pointless.
There are many who have researched the possibility of alien life making contact to pre-civilization and era of the pharaohs. I look at some of the writing and abnormal humanoid figures depicted in ancient times that differ from other deities that are clearly just a mixture of animals of the area.
Another thing to look at is the fact that today, we have trouble replicating and figuring out how pyramids and other structures were put into place back then. It would seem that there were either some greatly before their time thinkers when mathematics and geometry were in its infancy, these things happened serendipitously, or there was a more intelligent force that helped this process.
I always say when it comes to history and the mythical, it is important to look at similarities across different cultures. Just like how every culture has a flood story (thus we know that there at one point was a global rise in sea level) every culture has unidentifiable characters and distorted humanoid pictures as Gods. Some look very similar to other cultures that would not have had contact with each other in any way, shape, or form. I use that logic to base that there was a common event or being that was seen by multiple people during the same times.
I am not saying that life may not exist on other planets. Even though the chances of life existing on a specific planet may be very slim, there are so many planets in the known universe that it is likely many do have life. These life forms may range between simple life forms to life forms far more advanced than we are. What I am saying is that they have never come to earth. If they had, they would be the dominant species to this day as we would have no defense against them. Some may claim that they would no be here for conquest yet look at the habits of every creature known to man. Every life form from the basic bacteria to a human being does the same things. Carve out a niche, gather resources, then expand. Unlike you see in movies and television, mankind would not have a chance to win. Being more advanced, they would not send troops. Fact is, in modern warfare, we don't even send troops in first. We send in bombs, missiles, and drones. We don't send troop in until we can't reach the enemy with any other means. Odds are, if they are far more advanced, they would send a drone ship with weaponry to kill off all mankind in less than a day and then land in safety. Though we would likely be wiped out of existence, the invading aliens may decide to let some live. Well, I say "live" in a matter of speaking as we would likely be either slaves, pets, or cattle. Seeing that we are no wiped out, or suffering such existence, life from other planets has never come to earth.
The only plausible theory of alien life influencing the existence of mankind would be if an alien planet suffered some catastrophe that sent parts of their planet into space where basic cells may have survived being frozen as part of a meteor or other space debris. These basic cells may have thawed and adapted to life on earth and have been the first living cells that evolved into all life today. Some day, life on this planet will cease to exist but maybe a part of us will live on on some far distant planet afterwards.
God is not an alien, he is God. His so called "aliens" did not EVER visit earth. Only God has and there will come a day were he comes back. I am a true believer in God. For All of ya'll that do not believe in God, ya'll need Jesus.
If aliens visited earth, it's quite possible that humans could consider them gods. We have many anthropological first contact accounts where this has happened -- where the marvelous has been considered magical, so on the surface it seems plausible.
But mysticism and religion is almost ubiquitous, so if it were all explained by alien contact, there would have had to be a lot of contact -- in every culture no matter how remote, at multiple times in its history. Or else, if alien visitations aren't needed for religious belief, then religious belief is no evidence for alien visitation.
That's a negative refutation, but a more constructive refutation is this: wherever humans have visited anywhere new, we've had profound and far-reaching environmental and cultural impacts. We've discarded tools, packaging, materials and vehicles; altered the landscape to support our shelters; hacked, hewn, dug and killed to harvest resources; introduced exotic species; and altered the language, beliefs, customs, culture and epidemiology of whomever we've met.
Unless the supposed alien visitors are ecological and cultural ninjas, we should see a lot of similar evidence. But if they were ecological and cultural ninjas, how were they able to leave so little supporting evidence of visitation, yet so thoughtlessly introduce disparate religions to every culture on earth?
Lastly, we have modern proto-religions today whose foundations are well-documented, so we know that religions can develop without alien contact. So if human activity clearly explains the formation of some religions, we need a special reason to imagine it doesn't explain all of them.