It might sound odd for a Japan-only game to be my favourite. I played it a few years ago on an emulator with a fan translation and a couple things put it up on the list for me.
1. Town exploration was such a cool thing, being able to see a non-battle sprite walk around a town, talk to people and get treasure, make it feel like a more fleshed out RPG.
2. For an NES game, the story really grabbed me, and the last stage brought all that to a proper climax.
3. Celica is the OG grandmaster and a top-tier princess. Her Awakening appearance, I liked; but her class choice was a little messed up. Her Echoes design though, I think is perfect. The art style and design is both a fresh look and a throwback to the original.
I think Gaiden definitely makes sense for a remake though as it can now come out in the west and the new fire emblems borrow enough elements from Gaiden to (likely) make it approachable by both pre- and post-awakening fans. Also third person dungeon exploration? Looks just awesome, and I hope they have enough of it in the game to feel substantial. Also, a lot of the music in Gaiden is quite repetitive, but I find it quite catchy at the same time, and I think I'll definitely be listening to the OST on youtube the second they're uploaded (the one from the trailer sounds great).
If they had made this a Switch game, I would've instantly had a reason to get one, but its nice to have it come as a 3DS game (I have two) and I'm also kind of surprised that it's really not that far away from release! It feels like Fates just came out a few months ago. Gaiden feels like it would be too short of a game for the 3DS, so I definitely hope they add new levels/content as well from the original (Awakening length or bust). Either way, I'm really happy and the reveal had my jaw to the floor. I'm wondering, if Echoes does well, do you guys think there's a chance for a FE 4/5 remake, or are they too much of a risk?
In conclusion, this is definitely a day one buy for me; possibly even a Special Edition purchase (I've never bought a special edition of a game before) and a possible amiibo purchase (the only one I have currently a blue yarn yoshi).
P.S. RIP Alms package protector