Here's the pitch, cobbled together from a couple IMDB reviews.
An alien race from the moon lands in ancient Greece, terrorizing the nearby city of Samar, and taking the population’s children as human sacrifices. Hercules is summoned to oppose the evil Queen Samara, has made an alliance with the aliens in order to awaken a moon goddess and rule the world. Now it’s up to Hercules to save the day and free the oppressed townspeople.That's actually Maciste, not Hercules, but there's no appreciable difference. If you'd like some smarmy nerd humor to go along with it, check out the Mystery Science Theater version here.
Did you know that Hercules was worshipped as a 'personal savior' in ancient times? Did you know his Greek name is derived from Horus? Did you know he was the original celebrity bisexual? Or that he was the patron of Florence during the Middle Ages? Did you know that Obama sought Hercules' endorsement during his election campaign? Or that Hercules is the star of nearly 100 films as well as a number of TV series? Or that he appears in the most important movie ever made?
There are hundreds of strongmen in mythology- why is this one hero so popular? All I can say is that the Greeks and the Romans had a long time to perfect the character, so they must have done something right. Or perhaps it's because as classical scholar Walter Burkert claimed and Hercules arose from shamanistic trances and 'voyages to the underworld'.
UPDATE: Self-explanatory. Bonus factoid: Hercules took over the Hulk's comic book in 2007.
UPDATE: Greg is not an alien.
UPDATE: Shhh, don't ask or tell Frank Miller about this skit.