I tend to like them because to me they have a certain charm; the heroes are so earnest and stoic, there are no grey areas. They're kind of naive but it makes a nice change from more pessimistic fare. And yes, it's good fun spotting future spaghetti stars. One of the more amusing aspects is the casual jumbling up of myths and time periods. I recall seeing one years ago, think it was called The Witchs' Curse, where Maciste (in his mini of course) is sent a message asking for help taking on a witch so off he rows, ending up in Scotland in the Middle Ages! You've named a lot of the ones i like actually...though i do also like Hercules In The Haunted World a lot, also, i'd add Alone Against Rome, Revolt of the Slaves, Two Gladiators, Triumph of the 10 Gladiators, Spartacus and the 10 Gladiators, Medusa Against The Son Of Hercules and a slew of others. But i'm also fond of Sword and Sorcery films, Swashbuckler/Pirate films and those old viking flicks. I think they are just easy to watch and mostly entertaining.
You're right and personally i don't see anything particularly sexual in peplums, i just watch them because they're fun. And yes, i'd rather watch one of them than Prince of Persia too
I think the comment i made about not recommending them should have had more explanation. While i don't think they are "great" films (but ask anyone here, i hate calling any film "great") but i don't think they are bad either and when i said i wouldn't recommend them to someone i really should have said that with peoples' tastes these days i'd probably be hard pressed to find anyone who would give them a chance due to the bad dubbing, the low budget and the very simplistic stories. I think they are the type of film you have to develop an interest in and delve into yourself, if that makes sense.
But these kinds of plots crop up in all types of films. Look at your typical "fight" film. Hero starts of good, then success goes to his head and he abandons his friends or girlfriend, then gets beaten by the bad guy then bounces back for the big finale having learned a lesson. A lot of action films follow similar structures as do others. And actually when it comes to a lot of Hercules/Maciste films, they aren't known for their fighting skills....they are usually loathe to fight and seriously hurt people unless absolutely necessary. And these don't comprise all peps, if you want a lot of fighting, just watch the gladiator stuff, or ones with Roman legions etc...