Devil Summoner 2 has much better gameplay and more interesting story than the first game.

First of all, we have a roll mechanic -first game doesn't have it- and smooth animations in the game so the fights are more fun, demon compendium is diverse so the fusion system is impressive as always, i really love fusion system in the atlus games the bosses are forgettable and repetitive, i hate fighting same bosses, they don't offer a challange, they are just waste of time, Rate of random encounter is better, there is no random encounters in places like capital so investigations are more comfortable in these places,

to fusion special demons, you need to complete some sidequests

Soundtrack is great especially Battle Theme, it's my favorite.