I just finished my first Ys games, Ys I and II Chronicles on Vita. Overall I really liked them. The bump system grew on me, though I don't like that Adol was a glass cannon from beginning to end of both games.
The story and lore are great, probably the best out of all of its JRPG rivals at the time (assuming the story was this detailed in the original versions). The writing really shines with the character interactions and npc dialogue. Everyone you meet in the games has their own story to tell, and everyone eventually gets attached to Adol as well. I got a warm and fuzzy feeling at the end when everyone gathered together at the end of Ys II to thank Adol, and then this song plays after the credits:
https://youtu.be/UTfOvN8vLuo. I don't know if the Ys series has a main theme, but it should be Feena's theme...it's just amazing. Music is great across the board, with my favorites being Feena and the Ramia Village theme.
The dungeons can get pretty tiring with their multiple paths. Ys I is fine, but literally every area in Ys II outside of the towns is a huge labyrinth. It's annoying when you reach a dead end in a dungeon and have to backtrack to another part of the dungeon or a town to get an item you need to progress, and then you have to remember how to get back to the spot you were at. I hope that this design is just a holdover from the 80s and later games improve on level design.
Anyway, I can definitely see why so many people love this franchise, and I look forward to playing more of it! Origin seems to be the recommended game to play next since it's a prequel to the first two games, and it was conveniently released on Vita recently too. I'll get it when it goes on sale.