I feel like the way they were released is a relatively good way to play the games. The reason behind this is because each new title expanded upon the lore of the last one, adding a lot of new stuff to tie in to the other titles. Because of this, this is why the series always seems so convoluted; because ideas weren't expanded on until late into the series. If I had to give an honest review, though, this is how I'd play each title:
1. Kingdom Hearts- This one is a pretty obvious one to start with. Not only does it set a positive example for the other games, but it also sets the very base for a lot of story elements later on that you'd need to play this game to get (such as DDD with Ansem SoD).
2. Chain of Memories- Why this one next? Well, for one, the plot is still relatively simple compared to other games, so it sets another positive example for the series, despite the despised gameplay. Also, with Kingdom Hearts II, the plot of the game in the beginning will be a lot easier to understand than not playing the game first and playing the beginning segment with Roxas, so playing this title will not only be satisfying and "worth it," but it will also make the second game a lot easier to understand.
3. 358/2 Days- Why THIS one next? Now, if you know me well enough on these forums, you know I don't like this particular entry into the series, so why would I want to play it next? Well, for one, it gives a lot more meaning to the Axel-Roxas fight in the beginning of KHII, as well as shows some clarity to the fight between Riku and Roxas in the beginning of the game as well, as to why it happened and what was the aftermath of it, as well as explaining why Riku looks the way he does. So, this one makes the most sense to play next.
4. Kingdom Hearts II- This one is the easiest to play next. A direct sequel to Days and CoM, this game is pretty obviously the next one anyone should play. Easy story that directly connects to KH and its sequel games, this one makes the most sense to play next.
5. Birth by Sleep- Not only does this game tie back to the first game, it also explains the origin of Sora, Riku, and Kairi's abilities and Kairi's particular home world, but also expands the lore significantly and adds a new slew of characters that were never in the series before. Due to this fact of all of the new content that has never appeared before, I would not recommend this title early on, due to the fact that it is so involved and relies on previous lore to tie together its story. (play Terra-Ventus-Aqua order)
6. Birth by Sleep 0.2 -A Fragmentary Passage- This one, if it turns out to be a direct sequel to Birth by Sleep that doesn't get involved with the story-lines in Re:Coded and DDD, is the next one on the list. Since it deals with the drama that goes down after the secret episode, it seems logical to be the next one to play. However, since it may become involved with X or III significantly, it may move down to the spot right after DDD.
7. Re:Coded- If it weren't for the "reveal" at the end of the game or the secret ending, I wouldn't even recommend playing this one, to be honest. It can also be played before Birth by Sleep, if you don't care about small character reveals. However, since they DO show TAV, I would suggest playing it second, unless you don't give a flying fuck, like me.
8. Dream Drop Distance- Do NOT play this before its previous 7 titles I have placed here! DON'T DO IT! THIS GAME IS SO INVOLVED AND LORE-HEAVY THAT YOU WON'T BE SLEEPING FOR DAYS TRYING TO FIGURE THIS SHIT OUT, DON'T GO INTO THIS TITLE BLIND!!!! THIS IS YOUR LAST WARNING!
9. Unchained X/ X- These games, while relatively simple, are involved into KHIII, and they have a major reveal about the certain reveal of a construct character and his creature origin that tie to Dream Drop Distance, so, in order to understand why this reveal is so shocking, play Dream Drop Distance before this title. It is a free title, however, so have a lot of fun playing this one! This title and X Back Cover are interchangeable.
10. X Back Cover- Not only does this one have a different story than Unchained X, but it also is in KHIII's graphics, so this, much like 0.2, will be a sort of sneak peek into Kingdom Hearts III. This also ties into the story of X/ Unchained X, so this title and X are interchangeable.
11. Kingdom Hearts III- Definitely the last one you should play! With the reduced system number and the new graphics, as well as the fact that every title has been leading up to this, Kingdom Hearts III is a must-play for the last title in the series!
What do you think of this list?