People's expectations were too high. Also, the game had its flaws. Personally, I could live with them and I loved the game despite them. That said, I have a strong feeling they went completely wrong with XIII-2 - because of that feeling, I still haven't played it. It seems as though they listened to feedback but didn't have a vision to support it and as the result, the game lost the magic even XIII had despite its flaws. But I could be wrong because I haven't played it yet.
Hmm, Final Fantasy isn't alone regarding high expectations. Franchises like Resident Evil, that also were available during the PS1 era, are also getting a lot of hate this generation.
I think most people did not get FF13 right. It followed a new approach and FF 13 was very story intense and story driven. Square really took the story serious and that is one thing that most US games simply do not. FF 13 surely is not a game where you can have fun maxing out your character. But I think it was never meant to be played for 200 hours or longer. It mostly delivered a great story and there was put a lot of effort into the whole story. For me, the game was pure magic because I value story over gameplay.
Final Fantasy XIII had a nice ending, but there was one thing wrong with it that I realized after I was playing FF 13-2... The whole story of FF 13 was a lose-lose situation from the beginning. There never was a possible solution for this dilemma. Barthandelus has made a plan that would win every time. Either the characters defeated the Fal'Cie and Cocoon would die... or the people of Cocoon would start a civil war and tried to kill the Fal'Cie to become independant. Barthandelus would win in both cases.
The L'Cie where doomed anyway. They could either do nothing, become a monster and the people of Coccon would kill the Fal'Cie in a civil war destroying Coccon. Or they could destroy the Fal'Cie, fulfilling their Focus and turning into a Crystal while Cocoon would fall to destruction. So Barthandelus would have won in this case too.
Then there was the ending where the L'Cie decided to fulfill their focus, but two of them turned to crystal in a way that Cocoon was saved... but then suddenly all except Fang and Vanille turn into Humans again. And that was one thing that should never have happened at all. Once you are a L'Cie you are simply lost. Monster or Crystal, but never Human again. And so the ending of FF 13 contained the link to FF XIII-2 but I couldn't understand it until I have played FF XIII-2. And it made sense, but the Ending of FF XIII-2 directly has lead to FF XIII-3 and I am really thrilled to see how it will finally turn out in the end.
So if oyu have never played FF XIII-2, but liked the Story of FF XIII you should really give it a try. The Gameplay is similar to FF XIII, but as you are no longer a L'Cie, a public enemy, you can walk around the world freely. You can control only 2 Characters, Serah and Noel, throughout the game. As third character you choose from whatever Monster you can, but there are some monsters that excel at their roles, so you have to put much time into this monster hunting and developing. FF XIII-2 was much easier to Platinum and beat than FF XIII because there was no real timesink trophy.
The Storysetting is similar to FF XIII and you have yet again a really brilliant enemy to face. As long as you keep in mind that you will have a cliffhanger ending I am sure you will enjoy FF XIII-2 if you have enjoyed FF XIII before.