Devil Summoner 2 is a solid, competent, well-made, and occasionally lazy sequel that fans of both the franchise and the genre will love, though it might occasionally annoy more casual fans. The story is fantastic, the presentation is solid, and the gameplay has been improved in many key regards. There's plenty to see and do, and plenty of reasons to come back for more as well. This makes the game worth playing through not just once, but several times, if you like what it does. Unfortunately, it carries over a lot of elements from Devil Summoner 1 that either could have stood to be freshened up or didn't need to be carried over at all.
Some of the changes it made won't appeal to everyone. Devil Summoner 2 really is worth playing, and probably is worth owning, but it doesn't really manage to be anything more than "good." While that's not at all a bad thing, it's kind of disappointing that it isn't more advanced and enhanced than it is.