Apollo 18 is a good film to watch with someone gullible enough to believe it.
It's an okay film, nothing overly exciting - but good for what it is.
Going back to what might have happened during the lost 2 minutes on Apollo 11. I doubt they ever discovered Aliens. I doubt they found ruins either, something like that would be discovered too easily with the different countries that have landed on the moon. However I believe they saw something on the moon, something that NASA and any associated governments want to cover and hide from the public. So what could it be? The most popular theory is spaceships, but that sounds all too sci-fi to me, as I think events would have played out more dramatically otherwise.
Other possibilities though could have been a matter of them seeing figures looking at them, a bit like when in the dark objects can appear like humans or life-like beings - it seems like the most likely thing that could have happened. You can easily misinterpret things in the darkness. They may have even found a dead alien body or dead human (sorry, that's all a bit Apollo 18 now). But then I would guess something like that would be easily found out.
Dead human seems another theory that's slightly likely though - even though there are no manned accounts of the Soviet Union landing on the moon, they did make a few successful unmanned landings on the moon before NASA - could have they covered up a secret manned landing before Apollo 11 that may have turned wrong and resulted in a dead crew on the moon? I know it's a bit far-fetched, although I would never rule that out.
In summary though, will we ever know what happened during though two precious minutes? Simply, no. It could have just been problems with the cameras (even though I'm convinced it's a cover-up, you do not spend that amount of money only to have cameras fail for two minutes) or NASA could indeed be covering something up. But if hiding something is the true answer, it must be something big enough to have been kept so secretive the past 40 years.