I just finished Path of Radiance and kind of wanted to talk about the series.
Mine would probably be Blazing Blade or Mystery of the Emblem, BB because having some weird cult terrorist group as the villains was more fun than Evil Nation nº12837, MotE because i think it has some of the best gameplay and maps of the franchise while having a way better story than the other newer FE games (that i have played, Awakening and Fates).
Are any of the mobile phone versions actually worth playing?
I liked one or two of the GBA ones but was always more into Advanced Wars. Also if I had more free time I would make a lightly inspired clone of one of the GBA Advanced Wars.
If you don't have an addictive personality and can resist the gacha elements, Heroes is okay. But yeah emulating the earlier games is better.
you can emulate the earlier ones pretty easily on a phone, and those might be worth playing, but heroes is a gacha and you shouldn't play it.