Even though FIM isn't my fave generation, I really did love it (especially the show). I remember being blown away by the premiere of it--which I saw because I specifically got a cable package that included The Hub so I could watch it, LOL.
I am still amazed that Hasbro greenlit it, since the last thing we'd seen from them before G4 was the most godawful pony media in existence, the Newborn Cuties webisodes. ("My scawf!") Also just previous Hasbro was sending around internal memos insisting "Ponies aren't PONIES, they don't do ANY horse things. They are six year old girls. They do not do ANYTHING that six year old girls don't do." I still get angry thinking about how dumb and condescending that was. No one would say something like that about a boys toyline.
Anyway, I don't know what stars aligned to make Hasbro change their minds, but I'm sooo glad they did. The majority of MLP FIM episodes were really good, and even the ones that weren't good were usually "okay". (It had a couple stinkers, but what show doesn't, lol.)
Also: the music. Consistently great songs.
Spoiler
I watched the finale a couple weeks ago on WatchCartoonOnline--I didn't even realize they'd leaked early, I just thought they show had already finished as scheduled. Anyway, I cried a bunch.
I'm excited for G5, but I will always think fondly on G4.