The Ys III remake, Oath of Felghana is fantastic, uses the same engine/battle system, and scales up nicely with difficulty ( except for some bosses in Nightmare/Inferno mode). You can get it on PC/PSP
Ys Origin has a similar engine as well, although the difficulty scaling is not as good. That one's only on PC atm, but a ps4/vita port should be released this year.
There are also Ys III and Ys IV remakes on the PS2 that were published by Taito in Japan only, but they seem to be pretty subpar remakes for the most part, so I'd probably skip them unless you wanted to play through every single game.
If you're looking for a bigger world/story, apparently Ys VIII will fulfill that premise, even with a different battle system, and that should be releasing later this year for the PS4/Vita as well ( with the PS4 version apparently being the definitive version according to the developers).