I think it is a decent game but I don't like it any where near as much as the first game. It has certain "improvements" that people have been asking for, but to me they are superficial and not what is important to me from the series. Towns, sidequests (other than monster hunting), and minigames i didn't care for in the previous games in the series. Story and gameplay is what i mainly care for, and I usually ignored sidequests that don't have to do with fighting something, and minigames. I also didn't like large towns or castles because they always took to much time to get through to get back to the story or gameplay. I didn't like how the exploring is more like level select in this game either. The graphics were also downgraded in this game it seems. Some places look good, but overall it's not as good as XIII, including the character models.
I also didn't like how you are stuck with only 2 characters, that I don't like as much as the previous cast, and a monster. You are limited to only 3 monsters, where the main characters can have up to 6 roles. Also the main cast and the 3 monsters have less skills and less useful skills than characters in the previous game. Even though you can develop them how you like and they can end up differently, they still have less uses than the characters in the first game. Having 6 fully fleshed out characters give much more team customization than 2 static party members with less abilities and 3 monsters making up a 3rd member. Also I don't think the new crystarium is an improvement. The original had you think about what to get first, and the level cap made you rely on strategy to defeat enemies rather than overpower them with grinding. With all the sidequests in this game, you will easily overlevel.
And my main problem with this game would have to be the difficulty. It really is so easy, about as easy as Final Fantasy VII, which I consider the easiest in the series. But I think it poses more of a problem with this game considering the Paradigm system is made for difficult battles. In XIII you NEEDED to think which paradigms you needed and to actually switch between them in battle, in order to excel at the game. In XIII-2, cerberus (com-com-com) actually killed most of the random encounters the fastest. Casting buffs and debuffs were not worth it for most of the game even with bosses (unless you had that big goblin sentinal guy to cast all the buffs except Faith), and staggering actually took to much time in random encounters. Even the Long Gui was easier than the Adamantoise from the first game. Without the challenge, the Paradigm system doesn't work the way it should.
Being able to switch leaders in the party is an improvement I don't really care for. The leader dying not making you lose I didn't care for either. I played Shin Megami Tensei a lot so I was used to it (and in those games there are no retries). I don't like anyone dying so I always retry battles until I can come up with a strategy were no one dies anyway. But the instant paradigm switch IS nice, but considering switching paradigms isn't a big deal in this game, this improvement isn't a big deal either.
I also don't like how the game starts a whole new saga. It doesn't continue with the same themes of the first game, and is pretty much a completely different story. That said, it is interesting and Caius is a pretty good antagonist. But It's missing a good theme which is what I like about the previous Final Fantasies including XIII. XIII had a gnostic, anti-dogma, anarchy, Gallic War theme going on, and I REALLY loved that. XIII-2 still has the gnostic theme but it's still in the background and is missing all of the other themes.
I wont even get into how having to buy the DLC to get the full experience isn't right. But I will get into how the DLC is better than the rest of the game. It actually brings a bit more challenging battles. And the Valhalla Lightning DLC has to be the best part of the game IMO. I really like that fight. It's an example of what I was talking about. The fight is difficult (under level 9) and requires you to actually use all of your paradigms and abilities. This is were the system works.
The music is awesome though. Almost as good as XIII's soundtrack. Very close so I'm not dissing XIII-2's soundtrack at all. Except for Gogmagog's battle music (Limit Breaker or something like that). I will dis on that one. It's like Devil May Cry 3's battle music which I grew so tired of from hearing it over and over again, and Gogmagog is making me hear it again.
Like I said in the beginning, it is a decent game and I had fun with it. It's just that being the sequel to XIII, which is my favorite, led me to have high standards for this game.