OK, so in case you you don't know, Fire Emblem is technically a series, not jst one game. This games "proper" (read: Japanese) title is Fire Emblem: Rekka no Ken. The series finds you taking the role of a Tactician, who assists the main characters by commanding the troops. Incidentally, this game, Rekka no Ken, is the only one to my knowledge where the Tactician is an actual, named character who interacts with the NPCs.
Anyway, the game is Turn Based Strategy, meaning you tell all your units to go do stuff, then all your opponent's units do the same.
Of note is this: THE GAME IS HARD. Fire Emblem games are known for their unforgivably high difficulty at times. This stems from the fact that unlike other games of its type, say Advanced Wars, if you lose a unit in battle, there is no getting them back, they are gone for good, along with any weapons and items they had. The only way to "save" them is to restart the whole level.

(PS, if you want a REAL challenge, try FE: Radiant Dawn for the Wii, or FE: Thracia 776 for the SNES. The latter is JPN only, but some people have released a translation patch, if you have a ROM. I do not condone game piracy in any form, so you'll get no help from me in getting any of that)
----------------
REVIEW:

Graphics: 9/10
I love the graphic in these games, especially the GBA ones. They are vibrant, colorful, and clear. The details are superb, and they just look GOOD.

Sound: 8/10
Sound, well, it isn't BAD. It never, to me at least, gets dull or repetitive, and I LOVE the tune that plays when you recruit someone. A real shame they dropped that tune for the next GBA version.

Controls: 8/10
They are easy to grasp, and become intuitive after a few minutes. All in all, quite solid.

Story: 10/10
Well, I think the story rocks. The game gives you the 1st 10 "chapters" (levels) to get used to things and act as a tutorial, but dont worry, everything you accomplish in these chapters carries over to the rest of the game. Not to give anything away, but the story involves world war, evil wizards, ancient magic, and dragons!

Fun: 9/10
Well, if you are a Turn-Based strategy fan, you SHOULD like this game. Take note of the review title, though, this game can get HARD. See intro for the reason.

Replay: 9/10
With a "Hard Mode", as well as a 3rd campaign that serves as another perspective to the main one, you essentially get like 4-5 play throughs. a good value, I think.