Character development! It's something that Friendship is Magic does incredibly well. We have a group of six ponies that follow the usual personality tropes, but set themselves apart from the norm via a wide variety of quirks that draw you into their lives in a way other cartoons struggle with. Even the ponies that aren't a focus easily hit on that curiosity factor, especially the mysterious princesses.
Digibrony has released another video that delves into all of this! Head on down below to check it out.