As someone new to the franchise who's still catching up on everything, I can say that, at least from my point of view, what makes it fun is just that- it's silly and fun and campy, but there's still an earnestness to it all that makes the audience take it seriously. It's a fun little fusion of genres- you get that sword and sorcery fantasy mixed with more futuristic tech. Kinda like a kid just throwing all their toys together and playing. There's very clear-cut good guys and bad guys, with some really cool, fun, toyetic designs on both sides. Yeah, the names are ridiculous, but one could argue that's part of the charm too; they're easy for kids to remember so they know what to ask their parents for. It's not all that dissimilar from something like, say, Batman- Oh, the clown guy? He's named Joker. The guy with two faces? Two Face. What are the names of the guy who asks riddles and the guy who looks like a Penguin? Take a guess. There's a sense of whimsy that just doesn't seem to exist much in today's overly-serious society.
I'm not deep enough in to know about all the various incarnations and which are more serious and which are more silly, but that's any franchise- they reinvent themselves to match the times, and whatever incarnation comes next course corrects for the one before it. But like any good franchise of the 80's/90's, it's just about fun, imaginative escapism.
