Seriously? There's already another pony thread going on this very minute.
http://www.escapistmagazine.com/forums/read/18.284744-Is-My-Little-Pony-Friendship-is-Magic-good#11217496
However, I will repost my reply from there to here:
It's animation is great, its characters are fleshed out and realised without being stereotypes, the voice acting is phenomenal, the songs are good, the subject matter is excellent, they don't treat the audience like idiots, and the Creator Lauren Faust made it with the intent that adults will be watching it with their daughters, thus she didn't dumb it down.
Lauren Faust was also able to make this happen by telling Hasbro that she wasn't just going to make a twenty minute commercial for the toy-line and actually make people care about what they are buying. Plus, she's the one behind Powerpuff Girls and Foster's Home for Imaginary Friends, both of which are quite good.