Thanks for the feedback~ I'll reply for myself.
The first thing to know about My Little Pony FIM is that, at the beginning, it was supposed to be a show for younger people. The creators never expected to have, the large community that there is now. Even if the audiance of the show is ... actually, a majority of teens and young adults, you wouldn't doubt that they can't turn the show into something which would fit for this new unexpected community. The show wasn't supposed to be for them, so, they tried to keep the same fantasy, a fantasy which may attract both teens and childrens. Also, of course, older people can understand the morality before that Twilight has to say it, because we've experience on life, but younger ones ... should learn from it, I guess. We also know that it will ends well at the end of each episode, it's obvious that having a dark end shouldn't please to childs.
On my own side, why do I like the show... before-all, no, it's not because a lot of people liked it
One reason is that, it's cute, obviously. They're just cute ponies having adventures - it can maybe relate with Shojo animes. Some japanese animes are loved because of how they're cute, even if they don't involve story.
Another reason : ponies have an unique personality, but - they don't actually always stick to it. Fluttershy is deeply shy in the first episode, but through the progression, she gets more assertive, and even reflects the opposite of her personality in the 7th episode, where she protects her friends from a dragon. Supposed to represent the Elements of Harmony, they also display a contrast with their own personalities, like the Fluttershy example I mentioned above, or also the 20th one, where Rarity is jealous of Fluttershy, whereas she said that "a lady is never jealous" two episodes sooner, and.. I didn't even finished to watch the first season, but I also heard that Twilight becomes crazy in another episode. So- it's true that in the 5 firsts episodes, they seem to act according to their mental design, but they can do the perfect opposite too.
Universe is my main reason to like the show. Then, some people (not myself if you ask me, I'm not really into pony media) are interested by the animation of the show (which is a Flash animation if I'm not wrong), and then, the fan-made stuff. This goes through tones of
dubstep remixes on Youtube, as well as pony art, and why not memes. Usually, you must enjoy the show to enjoy the memes.