Ys IV: The Dawn of Ys indeed does rule. In fact, I have been playing it for the past day or so with the English translation for the first time and I am loving it more than I ever have. I am to the end now, so now I get to see what the ending is like in English
.
By the way, I assume you are using the translation patch right since you said the voices weren't in English but the rest of the game was? If you are, there should be a file in the YsIV.cab or whatever it was called that has a text file with the voices translated. It might not be as fancy as a sub, but it still works fine.
As much as I love Dawn of Ys, I still like Ys Book I & II just a
little bit more. Now that I have been using the translation patch, I love Dawn of Ys even more but the original is just the tiniest bit better. I like Ys Book I & II more mainly because of the fantastic story and music. Ys IV also has awesome music and a very cool and interesting story, but it just doesn't quite live up to the greatness of Ys Book I & II's music and story. However Ys IV has much better graphics, improved gameplay, and more exploration. These games are my all time favorites and I still have yet to play a game I think is better than these two (or three I should say).
For Ys III, I definitely say it's worth picking up, weither your a Ys fan or not. It's no where near as good as Ys Book I & II or Ys IV: The Dawn of Ys and that's mainly because it's nothing like them. Neverless I think it's still a pretty cool and fun game to play by itself.