For me, it’s one of two choices:
Final Fantasy VIII - It’s one of my favourite entries in the series and think they’ve ignored it far too much over the years. There’s a lot they could do with it, not just visually, but with the story and mechanics too.
Final Fantasy Tactics - This game is just fantastic all round, and I can’t say any more than that.
What would you choose?
Technically FFT Advance was available on the GBA, but it’s only the same game mechanically. IIRC the story is different.
FFTA is a completely different game with different mechanics. The job system, skill system, battle mechanics (judges), world building, playable characters. It really only kept the common theme between games like item and spell names. Oh and Cid.