I've watched some of the shows because they do actually lead to some interesting archeological digs I hadn't heard of before... However there's one thing that always nags me when watching this stuff -- why do they always think ancient humans were so stupid? It is believed that the human brain has not changed for around 100,000 years, which means that no matter how far back you go in our observable history, those people had the same capacity for rational thought as we do. Sure, we have a huge advantage through the knowledge of written history, but even a cave man had the same ability as we do to accomplish a task with the materials at hand.

You'll also note they always ask a modern engineer how they would accomplish tasks such as moving large stones, and the answer is always something like "I would use modern machinery" because of course we've come to rely on them and nobody today ever tries to think of any other way to perform the same task. How were the great pyramids built? They always claim it can't be done today, while conveniently ignoring all of the theories of how they did probably move those blocks.

So I guess my skepticism on those types of shows is that they intentionally leave out significant details to make everything sound more woo-woo (every big claim they make probably already has a wikipedia page providing legitimate answers or at least giving factual details). Sure there are some things that still aren't understood but just because you see some glowing lights doesn't immediately mean aliens are involved. Even though I do believe there is other life out there, I haven't seen any evidence yet on these shows that I would consider "proof" of visitations, but rather just a whole lot of "this is how we interpret the data to fit our conspiracy theory."