I think for the most part, it reminds us of the kind of television programming when we were younger. Television nowadays is mostly shit. The characters are interesting and we can relate to them, even if only certain aspects.
There was an online survey/census done earlier this year, with some rather interesting results about fans of the show: http://herdcensus.com/generalsurvey.shtml I don't really consider myself a "brony" as I'm just a fan of the show and some of the related artwork fans make. I don't buy the toys, I don't go to the conventions. I just watch the show.
Anyway, the joke behind the image I previously posted was one of the characters in the show styled themselves after the previous generation of My Little Pony. And is met with fear by her friends. It's amusing because the vast majority of the fandom hates the previous iteration of MLP.