This one has been a favorite of mine for ages. I also love the Gude Crest anime (which features the two heroines), and if you're thinking about purchasing the game, I highly recommend that you acquire said anime as well. It'll fill you in on the basics of the plot, though the game changes a lot of things and actually tells a much longer and more intricate story.
There are also plenty of cool, impressive bosses. In terms of attack techniques, they beat the Ys bunch hands down.