Haha, I hate the Lightning Saga but XIII-2 is probably my favorite out of the three. The gameplay is a lot more refined than XIII's, and I'm probably going to clock 70 hours once I platinum it.
I really dislike the villain in it. I like Caius as a character. He has plenty of layers and motivations but his reasoning is extremely flawed and despite his constant presence throughout the game, he never feels extremely menacing or like he should be feared as an antagonist. Trying to destroy time itself made him a threat that needed to be taken out, and he was very important to Noel and all of the Yeuls in time, but I can't get over how illogical he was...but that is what happens when you let emotions guide your decisions.
As for Serah and Noel, I really did enjoy them. They build a fast friendship, and do grow-up a bit throughout the game, but their development is very limited. They start the game hopelessly optimistic and end the game hopelessly optimistic until Serah dies as "New World" continues to play and chaos floods into the visible realm haha and even with the brief moments where they lose hope, I feel like they never overcame any personal struggles and instead just kept moving past them to try and reach their goals. It's not a bad thing.
My major complaints lie in the fact that they despite how much we see Noel, Caius, and the Yeuls, we really learn so little about them. Conveniently Noel is forgetting his life, Caius is now an asshole, and their Yeul is dead, so there aren't many chances to learn about them but rather their importance to the story and conflict. We get the simple rundown that Noel lives during the end of days as the last human, Caius was his mentor, and Noel was in love with his Yeul & Caius loved all of the Yeuls. I just wanted a bit more.
Also time paradoxes should not be the reason for everything. And that they didn't give us that Snow racing DLC that they wanted to make. And the bullshit that is the Requiem of the Goddess being DLC wtf stick that shit in the game.
Also that ending was wholly unnecessary. I still laugh about it two years later. (and a few days later since I actually finished the game this week.)
It's like a 7.5 on my list. I would probably not play again, ever, and immediately after I platinum it I'm selling it. 8D