Never again with that example it's a horrid comparison as I actually preferred DBZ to Kai just saying.
Well DBZKai cut out all the filler, so it was how it was supposed to be in the manga... but they sacrificed Gohan's voice actor, so I think it loses points for that...
But to be on topic, I don't think KH2 was bad, it just didn't live up to expectations and wasn't as good as KH1.
In terms of hackey-slashey gameplay, people need to replay KH1: it's just as bad: Vertical swing, poke, round swing (occasionally switch the first two). Switch it up by adding one more poke or vertical swing, and that's pretty much all you did for physical combat, unless you used an awkward ability. At least KH2 made it more flashy with different combos (but as others have said, that just makes it easier).
Magic system was also better in KH1, in my opinion.
And most importantly, Disney worlds and villains actually mattered in KH1. Princesses were being taken, Maleficent had a band of Disney villains doing her work, she was collecting the Ansem Reports, and corrupting Riku. Honestly, Captain Hook shipping Riku in his vessel with Kairi? That encounter in Neverland is one of my favorite in the series. Disney was nothing but a sidequest in KH2. Take out the worlds, replace them with original Square ones, and it works just as well. You couldn't do that with KH1. But to be fair, you could do that with BBS as well.