A mixture of great animation, well-developed characters, humor, good story, life lessons... etc.
plus a great community of fans just make this show awesome. Even though I was forced to watch it at first,
and had a very pessimistic view about FiM, I still found myself hooked by the 5th or 6th episode.
Friendship is Magic is a genuinely great show, especially when compared to all the crap most people watch.
That's why I will always be a brony, no matter how many people judge me or the show.