Is it necessary to play Dragon Quest IV first to understand what is going on in V? I was reading about the 4th one and wasn't sure if i would like the chapter based system, i mean playing different characters in each chapter. I kinda like having a main hero for the entire story.
I just got dragon quest V hand of the heavenly bride, and I havent played IV yet and I can tell you it doesn't matter. It doesn't start off from a previous story, and even the reviews of the game will tell you it doesn't matter. V is just sick.
It depends. If you want to play both of them it is better that you play IV then V. Dragon Quest V takes place in the same world, but many many years after IV. Although it has a history of its own, the things that happened in DQ4 have become legends, and will be mentioned sometimes.
You can play DQ5 without playing DQ4 though, but you're gonna miss the references, and if you play DQ4 after you will know some things that will happen.
Dragon Quest 1, 2, and 3 (the Erdrick/Roto trilogy) are all part of one world and Dragon Quest 4, 5, and 6 are all part of another (the The Zenithia/Castle in the Sky trilogy).
Unlike the Erdrick/Roto trilogy, the games in the Zenithia/Castle in the Sky trilogy are only loosely linked and do not reference each other in plot really at all, so you are not missing anything by playing them out of order.