Dragon Quest III was THE twist. It was the genesis of all twists going forward. It also in some sense, inspired the trope of Disc 1 final boss before discs for gaming was ever a thing. It also did what Pokemon Gold and Silver did long before those existed. It's a turning point in JRPG history. 

This is why I never buy a lot of the generic and nonsense arguments about DQ. People seem to decide what is JRPG history by their own gaming history and their emotions as opposed to a historical objectivity. The amount of things DQ did first (and in many cases, still stand up to time damn well) is staggering and doesn't get enough credit. Meanwhile, if I meet another person who pretends Final Fantasy X did switching in and out of combat first before DQIV (I have seen way too many people literally say or imply this), I'm going to tear my hair out.

DQIV's twist with what you think is the main villain was also pretty good in its time. This one probably meant more to the people back then, but it's worth acknowledgement. 

Then there's like, a lot of DQV. DQV's one at the top of the tower after reaching your home kingdom is brutal.