Which one? 7 or Sacred Stones? Although both are great!
7, I always forget the number since I knew it as just Fire Emblem while Sacred Stones I knew as … Sacred Stones.
I prefer 7 though since, imo, it's the best of those released on GBA, and I believe also the best released in any Nintendo portable system. Has a more extensive story, interesting lords, and didn't suffer from Sacred Stones's problem which was make the game too easy by adding an area for grinding and leveling up.