Grandia 2 is the obviously superior game of the franchise, and none of them are related so you can pick them however you want.
1 is pretty good, but its a bit simplistic in all aspects. The most interesting/weird aspect is that the main love story is between a young adult women and some 10 year old kid. But really its just a fun adventure game with a good combat system.
2 push the combat system... unfortunately its also crazy easy and you can breeze trough most of it without using most of the systems. I think the remaster introduced some difficulty setting, so it might help. But the real selling point is the story, or more specifically, one of the character in the story, its the only game I strongly recommend playing with english voice acting. You have, iirc, the little mermaid, just chewing the scenery and having a great time playing as this succubus-ish demon women, its great and worth playing just for that.
Then there was extreme, I recently replayed trough it again, but honestly, its just a so so game. Its a very pare down game, barely a story to speak of, there's only two town in the whole game (and one is barely one), so you just always go back to the same one, very little world building and progression. Most of the game are going trough these massive dungeons that takes a really long time to go trough. Thankfully the combat system is really good, difficulty was increased from 2 and there's a lot more character customization to be done, with a somewhat deep skill and magic system.
I played trough it again because the first time I played it, I didn't use a specific character who's the only character who can steal in the game. Turn out, the post end game is this massive 100 floors dungeon, and to get the best equipment, you need to steal them, but character not in your active team don't level up, so I remember as a kid being massively bummed that my progression trough the dungeon was hampered because of that and I dropped it. So I wanted to try again to really finish it. Turn out once you get to floor 100, all there is a short cutscene, no super optional final boss or anything...
3 is... look I remember almost nothing about it. It was okay I think? But really not memorable. The only two thing I kinda remember is that it played the tropes of "mystic girl fall from the sky onto main boy lead" straight and there was a cool subversion of the usual parent tropes, where the main character mom join him on his early adventure as a playable character. So you think she'll die at some point, right? Nope, she just find herself a boyfriend and just tell her kid to do whatever he want, she'll just settle down. I would like them to remaster it just so I can replay it and see if there was anything interesting about it, I'm sure the gameplay was decent.
(there were some gameboy games somewhere, but never played them)
Anyway, fun franchise but also show that turn base JRPG combat can be pushed more even back in the PS1 era, so its a shame most of them never really did anything more with it. Would love some sort of spiritual successor.
