@takashichea: KH2 was a true sequel. It was completely superior to KH1 in everything.
This is completely true. After playing the first game, I really grew to appreciate the improvements that were made in KH2. The improved camera alone makes it a superior game, but they also added in other stuff such as greater mobility for Sora.
That said, I remembered I had mixed thoughts on the game the last time I played it. I remembered that I disliked the game for being too easy and for having too many QTE's. I will probably like it alot more now that I relived Kingdom Hearts 1.
And the fact you could use 3 characters with very different playing styles made for a very good gameplay element
And there's a good chance they will be doing the same in Kingdom Hearts 3. I think they were hinting that in Dream Drop Distance.
@takashichea: I found Kingdom Hearts 2 emptier and it was harder to manage Goofy and Donald to me personally. Cloud was the best AI ally I had. He just couldn't stop killing things and letting me have kills. I never beat Kingdom Hearts 2 yet.
Goofy and Donald may have been harder to manage, but they healed you more often and they died alot less. That is good enough for me. Regarding the empty environments in KH2, I generally found that the environments were huge compared to KH1. Perhaps you thought they were empty because there weren't enough enemies and NPCs to fill that increased space.