Dragon Warrior III basically perfected the gameplay of the series, so Enix wisely decided to try some new things with Dragon Warrior IV. As is often the case with new ideas, some were successful, and some less so.
First and foremost (the subtitle of the game is “Chapters of the Chosen”) is the chapter system the game uses. Story-wise, this is great. You spend four chapters introducing the characters that will eventually team up with the prophesized hero, establishing their character and motivations. Each has a strong connection to the plot and at least some justification to why they would join the hero. And the stories told in these chapters are quite good on their own: related to the overall story, but generally pretty self-contained.
The downside of the chapter system is that you need to level characters up from level 1 without help four times. RPGs are often fairly boring in the early going, since the numbers are small and you have few abilities. DW4 does as well as you can with the situation, with a wide variety of low-level monsters between the chapters, but it still turns into a bit of a slog in the long run.
This is the first game in the series to have actually named characters, and they do a good job of filling in the roles of DW3’s classes. The basic melee classes are each covered, but the wizard and pilgrim classes each have their abilities largely split between a pair of characters. Once you have the full party, and the ability to (in some locations) switch between party members during battles, this design really starts to shine.
As cool as the wagon and character switching are, they come with the AI system, another cool idea that doesn’t work so well in practice. Unlike later versions, you don’t have the option to directly control every character, meaning that in chapter 5 you only control the actions of the hero. The party AI isn’t bad for random fights, and it speeds up the game considerably when exploring or leveling, but your characters waste a lot of actions and MP trying to kill bosses with death spells or use other tactics that are doomed to fail. It’s even a problem in certain normal encounters where you need to focus on particular monsters first and your party just isn’t interested in doing so.
The story is one part of the game I have no significant criticism of. The chapter stories are cool, and in the final chapter you learn that the bad guys are just as aware of the prophesized hero as the good people of the world, and are acting against him or her. It’s a nice take on the hero legend which will carry forward into at least DQ5. They subvert the hero trope in a few non-obvious ways that I enjoyed, but I don’t want to get into spoilers.
The villain in particular is quite good. Unlike previous series villains, this one actually has motivations and they even build some sympathy for his point of view. Rather than the usual big bad priest who wants to destroy everything, we get a bad guy out for revenge and gathering his power similarly to how the hero is. The story leads to a satisfying conclusion that plays off your expectations based on the previous games’ tropes.
Finally, there’s the gameplay. Largely unchanged from DW3, aside from the AI system, the gameplay is solid throughout. However, the game does offer up a few too many dungeons in the late going, and I found myself questioning what to do at several points. In particular, there is a tough boss that I figured I’d have to defeat later (which I did), but the game offered no actual advice that that’s what I ought to do. Considering how hard the AI system makes bosses, I really have no idea what the game was intending for me to do, even in hindsight.
All in all, DW4 is a very good entry in a very good series. Enix could have rested on their laurels and just made another DW3, but they changed enough to make DW4 its own game. Not every change worked, but advancement is rarely strictly positive. I still prefer DW3 in general because it has less flaws, but DW4’s story is certainly the best in the series to this point.