I find tem very entertaining but, what's more interesting, I love to try and find out where they come from, how the story got progressively wilder etc. Call it sociology or studies in folklore, that's a great way to understand how our brains and social relationships work.
About the Devil's dumbness in many of these stories... we should talk about it more in depth sooner or later but I personally believe that many of these originated in the the first millenia of official Christianity (but probably much later: still in the XVIII century more than a member of the Lutheran Church of Finland was tried by his superiors for practicing "pagan" rites to ensure a good catch for the local fishermen). Missionaries often had a very hard time cracking "pagan" cults in the areas away from big cities and so resorted to implanting a few fanciful stories of their own, ridiculing local deities and demigods (ie the Devil). But that's another story for another day.