Digital Devil Saga 2 is nowhere near as effective without the character development portrayed in DDS1. The storyline of DDS1 might seem somewhat small once the series segways into the second game, but really, you need to experience it. The exposition helps tremendously.
It's entirely mandatory in my opinion.
I second that. Definitely.
It's hard to describe exactly what makes nocturne so great. I guess you really feel you're part of that world and that you can make a huge difference in it. And what a fascinating world it is. I replayed it recently and enjoyed it even more than the first time. I really like the wole concept.
At the beginning you're having a normal day with your friends and end up being one of the few survivors of the end of the world. Seing how those characters developed, the vision they had for the new world, the methods they used to aquire the power to accomplish it, the way you could shape your relation with them through the course of the game, choose sides or restore the world back to normal. or being mocked by the god of that world and deemed unworthy or just becoming the friggin' lord of the underworld taking lucifer's place, the way the game puts all of that into your own hands, is what makes it so great.