Dragon Quest 4 and 5 - if you have not played them - are amazing. 5 is one of the best RPGs I've ever played. And 4 on Ios has the party chat that the DS versions of the game did not include so it may even be the definitive version in the west.
If you like old school, 90s PC era style RPGs, Dungeons of Chaos is great and has a metric ton of content. It's very old school though, but I love it.
Tower of Fortune 1/2/3 are Gameboy looking adventure games where you use a slot machine mechanic to do battles. It's a really weird thing, but the games are a lot of fun and I never see them talked about.
Final Fantasy Dimensions 1 - have you played this? I've played a few hours and it is like a FF4 type game (the SNES one) and seems pretty good.
Another Eden has music by Yasunori Mitsuda and is a time travelling RPG. It is way better than it has any right to be. Look up some videos - I've had a good time with it and played about half the game.
The Quest HD : First person old school RPG set in a huge fantasy world. It's got a lot of content, big overworld to explore with lots of dungeons and cities etc. It's turn based. Very good game
Siralim 3 : This is another old school sensibilities RPG that also has monster catching/levelling in it. The game has Disgaea levels of customization and content. Hundreds of hours probably. It looks very basic and plain but the actual game is very very fun.
Sorry for the random ass suggestions. There aren't a ton of classic turn based RPGs that I have found on Ios that are like FF and Dragon Quest. But I've had fun with everything I listed above. Hope you find something!