Friendship is Magic has a lot of great talent work done in many, if not every, aspects.
The characters, both primary and secondary and even antagonistics, are extremely well written and unique on their own, coupled with memorable cast and voice acting.
Animation, models and backgrounds still improving ever since. The difference between S1 animation [which often re-use the same models] and S8 is stunning.
The music goes way beyond simple sound and instead captures the mood and feelings in each moment, and the songs are worth to listen to.
It may look like a kid's show and it may have its own downs... but you can see it is a show made with heart, passion and care.