What Fire Emblem shines in is it's amazing RPG feel, great story, and the ability to save or lead characters to death.
Yes with the Wii, Ds, PS3, PSP, and Xbox360 out it is hard to go back to GBA games but this one is one that should be in your second Ds slot. (It is in mine)
If you like to customize characters, really get in to a story and feel sad when somebody dies then Fire Emblem: The Sacred Stones is the perfect game for you. Every decision you make could be your last. That is just one of the most amazing things about this game.
But getting in to more detail. You can have bowman witch have a larger range for attacks there are swordsman who can attack only whats infront of them and move a few spaces a turn. Horsemen can move plenty of spaces a turn and are harder to hit and can only hit whats infront of them. There is magic. RPG elements all around. Certain magic and super effective to others and there is healing, trading items, armories, and tournaments witch you can enter and win money. But be carefull with your characters because each life is important.
You can tell they really put some time in this game and it turned out great. Fire Emblem: The Sacred Stones gets an 8.5 Great.