Speaking of emulating the game, there's a fan-translation patch for both the PS2 Final Mix versions for Kingdom Hearts 1 and 2.
Final Mix KH1 adds a couple new enemies, as well as a higher difficulty. Gummi Ship routes also get missions to try and add a bit of incentive to play them more and actually build a good ship. Enemies also get a palette swap to some really interesting new appearances, and Synthesis supposedly has some new stuff as well, both new ingredients and new items to create.
Final Mix KH2 gets a TON of additional boss fights (including every character seen in Chain of Memories as optional bosses, as well as turning a particular cutscene battle in the final world into a kick-ass fully-fleshed boss battle), a higher difficulty level that tries to change how the game works strategy-wise (Sora has half HP and overall lower stats. Enemies and bosses get additional HP and higher stats, to near-unfair levels. To compensate, you start the game with a bunch of abilities as well as 50 free AP to distribute). A new Drive Form is added, called Limit Form. It doesn't require losing Goofy or Donald, and it swaps Sora's appearance and moveset to match the first game. Your shortcut menu features all of the special attacks like Strike Raid and Ars Arcanum, and your level-up skill is Dodge Roll, meaning that you can unlock Dodge Roll for Sora's default form.
Both games also get additional cutscenes, but they aren't voiced since the voice actors had aged enough that there would be a huge difference. (Compare Chain of Memories with the original Kingdom Hearts for a good example)
Finally, regarding Kingdom Hearts II: Final Mix, there's one more thing that's probably the biggest draw overall. One of the abilities you start the game with is "EXP Zero". What this does is remove the level-up system entirely from the game while you have it active. This means that you'll be playing through the entire game at LV 1. Even better, this ability is only given to you when you start the game in Critical Mode, the new super-difficult setting.
I've been playing KH2 in Critical Mode, but without the EXP Zero restriction. I got all the way to the final boss, but the last form is able to one-shot me and I can't quite figure out how to dodge the attack reliably enough to beat him. I kind of left it at that and started playing some other games, but I eventually plan on level grinding up to be able to at least have the opportunity to heal after taking the hit. (There's a new ability that's essential for Critical Mode called "Leaf Shield" that prevents you from taking damage while the Cure animation plays. I don't recall if it's in the normal game or not, though)
If you want to try emulating the two, the translations aren't very hard to find. (at least the KH2 one. It took me a while to find the KH1 patch) If you want to go with the official version, the HD remasters are based off of the Final Mix versions. Birth by Sleep has a Final Mix version as well, along with a translation for it too. I haven't played it enough to see the differences, although I know that the Mirage Arena gets a bunch of new fights, including a fight against Monstro. PPSSPP doesn't have a way to get multiplayer working, though. At least, the last time that I checked, it didn't. Normal BBS does work for multiplayer, for some reason.
Edited by kurt91, 16 March 2017 - 06:00 AM.
