For me personally I'd have to say its the Character designs. I feel that even if the story may be boring, at least the characters look fun and interesting. But enough about me what about you?
it’s the music for me. Fates OST blew my mind away. I liked some of Awakenings as well, ‘Don’t speak her name!’ was my favourite. If it wasn’t for the music, I wouldn’t of put 1000+ hours into Fates (I played Conquest twice and Revelations once). My to-go battle music that I enjoyed in Fates was A Dark Fall.
Probably the promotion system.
Even though it's a bit boring after some time when you know what you can promote into, the first time I played a Fire Emblem Game (SS) it was the best thing ever.
When I got Ewan in my first playthrough I just thought "Oh well he'll probably be a boring mage".
But then when I promoted him I saw that you can choose between mage and druid and I was like "Holy shit, I can make this kid into a dark mage. Best day every."
After that I proceeded to destroy the whole game with my SM Joshua and Dark Overlord Ewan.
Having the choice to choose into what your character progresses (even though it's kinda limited but still) into is still one of the coolest aspects of Fire Emblem for me.
Really it's a mix of many factors.
-A large cast of interesting side characters (not just fodder like many other strategie games have)
-Good story, that doesn't rely on 101 twists in it, like many JRPGs have.
-The strategy that's easy to learn but hard to master. A kid can learn FE, but many adults still struggle with it.
-Overal design, a nice balance between fantasy and realistic. It's still very JRPG, but it never goes too strange.
-And more..
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes