What I didn't like was the whole Nobody thing. The Roxas drama wasn't very interesting to me. And Sanctuary made me eat orphan newborn babies to keep down my nausea, as I've stated before.
The most frustrating thing to me was that there were a ton of mysteries in the beginning, and all the revelations are crammed in at the very end. It was a long middle to go through, hoping to find out the answer to the questions along the way. But no. Nothing. The game was too long and too easy.
That, and it was in Sora's point of view only. In KH1, we got rewarded with a scene showing what was going on with the villians once in a while, after every other world. In KH2, you're stuck with SDG going through rehashed worlds with boring plots.
They could have had scenes with point of views of the many characters they introduced. Namine, Roxas, Axel, Kairi, Xemans and the rest of Org13, even Riku. But no, no break from the long dullness of going through rehashed worlds and boring plots with SDG. *Sora wasn't an interesting character in his game either*
This game had potential. They just didn't use it, for some reason.