From favorite to least favorite:
1.Birth By Sleep. There are two main factors as to why this is my favorite. First off is the presence of debuffs. This is a HUGE factor to me in terms of enjoyment of RPGs. The most we got in the past games is Stop in KH1, which was nice, and Magnet in KH2 which was...OK. Here, we have Sleep, Stop, Mini, Poison, Slow, and I loved experimenting with all of them. The other reason is because of Terra's story. The worlds felt like they more relevant to the story. Not so much the 2nd half, but more of the first half. They kind of dropped the ball with Aqua's story, but I can't ignore what I love about it.
2.Re:Chain of Memories. This is so high up on the list because of my impressions after playing KH1. Here, I actually cared about Sora! I was curious as to what was going to happen since it seemed like it was going to go into more detail about what happened on Destiny Islands, which we thought we knew about. I just couldn't help but feel bad for Sora. As for the card mechanics, I had to force myself into it at first, but I grew to really enjoy it.
3.Kingdom Hearts 1.(Only Final Mix) When I first played Kingdom Hearts 1, I didn't think anything special of it. Didn't care much for the story and the battle mechanics were OK. Then I started exploring, and I realized just how much I was missing out on Final Mix's content. I love the unique enemies and how you obtain all of the synthesis ingredients, such as with the White Mushrooms. I daresay this game has the best farming mechanics out of any game I've ever played. I haven't played the original, and from what I know about the differences between the two games, I don't want to.
4.358/2 Days. This game had so much potential. I cared more about the bonding between Roxas, Axel and Xion FAR more than I could ever care about Sora, Riku and Kairi, but the plot is really lacking. It would've been much more interesting to see more objectives, along with more missions for Roxas to go on along with other members of the Organization. I admire the potential of this game more than the game itself, but I do like what we got. I enjoy the panel system since I'm a sucker for different methods of customization, and I really some of the song remixes here.
5.Kingdom Hearts 2. Unfortunately, even Critical Mode didn't do THAT much to save the game for me. There are 2 main problems. First is the gameplay. Critical Mode did make it more fun, I'll admit that. However, my main issue, admittedly bias, is that the game chose to be an action game first and an RPG second. KH1FM had a lot of abilities that made me take my stats and equipment into account, along with farming for certain items to increase certain stats. Here, it's just a mindless process of beating the crap out of anything. While that is fun, the RPG elements are really lacking. Boosts from armor and accessories felt negligible outside of gaining AP, and they completely got rid of tech points/weaknesses! Why would they do that?!? As for the story, I love the ideas, but the pacing is terrible. There's the Organization's goal, Axel's plot, Roxas's story, the Disney worlds's stories, Riku, DiZ, it's all over the place. I wouldn't mind it if it were told better, but it wasn't. I do enjoy Critical Mode since it gives a thrill to the battles with the risk of dying, but that's it. I've yet to go through the Cave of Remembrance, though.(currently working on Mushroom XIII first) I have had fun with certain bosses, and I feel like the Data battles will be interesting.
As for Coded and Dream Drop Distance, I've yet to play either of them.