Fire Emblem is very different from FFTA. IMO, Fire Emblem games make you think more, since you can lose characters permanently (plus other elements), and have a really interesting story. Shadow Dragon is pretty good, not as good as the original GBA one, but still very good.
Also, you could try the Advance Wars series (Dual Strike and Days of Ruin). Both are tactical RPGs, somewhat similar to Fire Emblem in the interface. You don't need to play any previous GBA Advance Wars games (even though it could help a bit I guess for Dual Strike, but Days of Ruins is an entirely different story line). I liked Dual Strike more, but Days of Ruins is nice as well.
Seconding Elite Beat Agents!
Also Feel the Magic and The Rub Rabits for more fun, weird games!
Kirby Superstar Ultra is really good. If you didn't play the original SNES one, then get this NOW. Best Kirby game ever, and it's really fun. Oh, and Kirby Canvas Course is fun too, even though it's a very different style of play.
I enjoyed the Final Fantasy III and Final Fantasy IV remakes, so look into them if you like RPGs. Same with Dragon Quest IV and Dragon Quest V.
I've always been a Mega Man fan, so I recommend Mega Man ZX. Didn't really like the second one though.
And if you ever get the craving for a fighting game, the Bleach DS games are the best fighting games available on the DS. Even if you are not a fan of the series, these are really good fighting games. They were developed by Treasure, so you know it's good!