I know. Legend and Adventure were Saga and Mana :] But he didn't say GameBoy "Advance". So I figured I'd ask to clarify.
If we are talking about GBA remakes, the only one I've played is Dawn of Souls (FF1/FF2). And I haven't played FF2 on that yet. Though for FF1 I seriously don't recommend it. Personal taste really. It lost the charm and feel of the original in my opinion. If you want FF4-6 I would personally suggest the PS versions and get some nice CG out of it and bigger screen. But again, that's personal taste.
FF3 however is probably hands down the best idea for getting a remake in the near future