Short answer: I think he's neat, and that other people should think he's neat.
Long answer: Because of Marth being the first protagonist of the first game ever, and said
game being released in Japan, the first exposure the West had of him was in the
Super Smash Bros. series, and for me,
Super Smash Bros. Brawl. I was really young then and didn't
know about the Fire Emblem series at all outside of very surface level knowledge, and I had
never really seen advertisements of it, since I lived in a country where accessing games
meant pirating games mostly. I only got into the series due to
Conquest and then
Tokyo Mirage Sessions, and even in that game I mainly just...
didn't care about Marth really.
Then Heroes and Warriors came out.
Though the latter game had given Marth some much needed exploration, I felt that my
indifference towards him was mainly due to me caring more about the
Fates roster in the game at that time, and that
Heroes didn't do a good job portraying him as other than 'good
generic chosen one #1' at the time (the exploration potential of
Heroes vs what they actually do... a rant for another time).
Keep in mind that I thought Fates writing was actually good at
that time, and also was never really aware of his depiction of the
Shadow Dragon remake.
It was only when Engage came out that I started to care for
Marth. Hhe was there in the beginning and has such a sweet relationship when he was
on-screen with Alear that I couldn't help but be drawn to them and him; even with Alear's
memories missing I felt like they had a natural chemistry and history between one another,
and during Chapter 10 where Marth gets ring-napped, I started
to joke in the place of Alear, making them say
'where Marth' until you reunite with him in
Chapter 21.
I'm a weirdo who attaches to characters that have angst, and especially when it's a
self-sacrificing hero who fights for what they believe in, like Marth. Looking back at his
conversations in Engage as well as
Warriors as well as Heroes and his
home game, I can say that he's a really sweet charaacter that just wants the best for
people. I love it that despite being royalty, he sees himself and his friends from all
backgrounds as equals; that he tries his absolute hardest to make people happy; that he's
humble, and knows that he's not that strong nor wise, but his charisma and honesty makes him
an ideal, shining beacon for people to rally around for the greater good. He's endured a lot
and recognises that he's not a saint, yet tries and shows mercy - killing only when
absolutely necessary.
I think I also admire him for his resilience despite tragedy and trauma. He (seemingly) lost
his family and his entire Kingdom overnight, and was forced to flee his home, exiling
himself to Talys until two years later. Even when taking back his Kingdom from Gra forces
and Dohlr, he had the chance to be vindictive to said Kingdoms, but didn't. Even in the face
of overwehlming trauma and anger, Marth still chose to be kind to his enemies; it's
something I wish myself to be like, and hopefully one day be a shining star in my friend's
lives just like him.
TL;DR I think he's the goodest Fire Emblem boy, and I hope you
now share my enthusiasm towards him too!