>>3787832 (OP)2 is really great. Though Nisa did a terrible job translating it and actually introduced a bug into the game during a boss fight that crashes your game. Luckily though the game is easy enough you can smoke the boss before the game crashes. Otherwise the game has a great story, characters, music, setting etc. It's way above par for gust.
1 is also very good. But not quite as good as 2. It's more generic in general. I love 1s box art though it always makes me nostalgic.
I've never played 3 because I didn't have a ps3 and it's never been ported to anything else. AR tonelico was great and gust is still alive and kicking. No idea why we haven't seen remastered collection yet for the series. They did several for Atelier trilogies...