Originally Posted by
Aeolus Aeneas
The DS version of books I and II is basically broken, as the company that did it (which wasn't Falcom, because if it was they would have NEVER screwed it up) added an attack function while putting the ramming of the original as a touch gimmick meaning that to do it the proper way, you gotta use the touch screen, and that's a pain in the ass. They also added a new area and then didn't bother to rebalance the others, making you overly leveled after the fact. Plus, the new area is pointless anyway, as they didn't bother to rewrite the story to take it into account, so it's promptly dropped and forgotten about.
PSP is the way to go, as it has (coming soon to the US) ys 1 and 2, Ys 3 (Oath), Ys 6 (Ark of Napishtim) and Ys 7. There hasn't been a remake of 4 and 5 yet, so you'll have to go to other systems, most notably the SNES (though 4 isn;t that great, and I haven't played 5 yet), though there are other consoles they appeared on.
There's also Origins for the PC (no clue on fan translation status of that), an MMO (again, not in English), a strategy game and a crossover game between Ys and some other series which MIGHT see the light of day, as supposedly the game series it crosses over with is going to get an official release.