Beyond the obvious bullshit that is the TV show, "hey look holes in a rock, must be high tech!" There is still evidence that ancient man was more advanced then we are today, but does that mean that aliens visited us? All the religions of the world talk about things descending down to interact with humanity sometimes giving individuals divine right over kingdoms. There are a lot of interesting alternative researchers out there like David Icke and Jordan Maxwell who are well known and often criticized, but I've stumbled on a new guy who's a lot better as researching and source citing goes. His name is Joseph Farrell, and his videos about a Cosmic War are fascinating, but what he really does good at is bringing up tidbits about Nazi Germany during the end of WW2 and all the sneaky stuff the Nazis did.
So what do you think about weird stuff the Nazis did and brought over to America, and what do you think about experiments America did themselves? If you're not sure what America has done, look into things like the Philadelphia Experiment or project MK Ultra.