Never claimed it was difficult, just that it was unique and that you couldn't win by spamming the same two buttons the entire time. It's something that you won't necessarily be expecting the first time you run into it, and fairly fun.
Luxord, maybe, but Xemnas?
Axel? Demyx? Xigbar?
Well, ESPECIALLY Xemnas. His was, like... what? "Press Triangle when something is blocking you, then get near him with triangle, THEN spam your cross, repeat until bored. After that play Gradius 3D (or was it before?) "
They're awesome (and in case of Sephiroth, badass), I have to give them that, but it's because Sora and Riku are even more flexible than Neo in his own Matrix. Take that part out and they're really just about button mashing (except Luxord, as you mentioned)
The motivation, at least on the part of the protagonists, is all about devotion. Sora is so devoted to Kairi that he will turn the world upside down twice over just to save her. King Mickey is so devoted to his responsibilities that he's willing to endanger himself and do leave behind those he cares about in order to do what has tobe done. Riku is in the first game devoted proving he's as good as Sora, and in the second game to redeeming himself.
It's too linear. I see that Sora's heart is in the right place, but he did all that not because of a reason. He simply did what he thought is best. The same goes for the other characters
I mean, they don't have any goal that they knowingly have, if you catch what I mean.
Let's break down their motivations:
Sora: "Kairi is in trouble! I have to save her by going to random worlds and smash thing up!"
Riku: "Damn, this guy is catching up with me, better do something awesome and stupid then"
Mickey: "The world is in trouble! I have to leave everyone clueless and watch from afar as they look for me!"
Donald & Goofy: "The king is away! We'll have to leave the girls alone and defenseless as we look for that stupid king!"
Organization XIII: "I want some heart, and bad. Let's throw some unfathomable plan and watch as they fail"
Pete: "I want to rock the party up! Let's take some random power the protagonists don't have and use it to fail!"
My awesome and badass Sora, the very guy who defeated Sephiroth, can't just capture Pete, because of what? Because the goddamned guy can freaking
teleport! Between worlds I have yet to open! And where did he get that kind of power? Nobody had an idea
What is with this development? It's like Power Rangers or Super Sentai, where the bad guy gets a mechanism to go overdrive or something after he's defeated. If a weak obese guy can teleport, why can I only skate? If he can control the bugs in Re:Coded, why can't I? Especially after he crafted a freaking genie lamp with that?
It's not fair (and plain ridiculous) is what I'm saying. I'll trade Neo's flexibility with teleportation anytime