A lot of people dislike Ys IV on the SNES, and prefer the PC-Engine version, even though the remake of Ys IV was based on the SNES version.

Personally, I've only played the PC-Engine version of Ys I all the way through. I got decently far in Ys II, though. They're certainly very different from the newer games, so you might be more interested in the remakes and genuine newer entries.