Sora needs major character development, not to the point in which he's unrecognizable, but he needs something. He's too lenient and light-hearted for his own good, and he is a bit too naive. In KH he could get away with that because he was just tossed into his adventure and was just given a big ass Key as a passport to go travel. On his adventures he learns about the depth of the heart and comes to understand the complexity involving the light and the darkness, and their effects on the heart.
In KH2, he seemed a bit dinky in comparison to how he was in KH... And his overly carefree attitude kind of dampened the experience. In a way, he was kind of lesser in KH2. I thought he'd take things more seriously and pop up with some ground breaking quotes (like he did in KH) based off the kind of experiences he had gone through. Instead, Organization13 screwed with his head, Sora seemed not to gather things as quickly, and he was more, or less running on mental capacity in comparison to that of Donald and Goofy...
Riku had great character development... He seemed the most complete out of the initial trio. Then again, anything's better than Kairi. So, Sora wasn't so bad if we take into consideration that he was asleep for one year (that would hurt you socially)...
In KH3, Sora needs to be more than just a guy swinging a Keyblade to defeat enemies in his way. Like, I wish he questioned more about why he was chosen, question what his actions have on the worlds, as well as taking into consideration of the pros and cons for slaying things, and for the final bit, just a bit more serious about how he goes about things.lol