Oh boy, time to make a few people happy and a lot more sad. I have a confession to make, Kingdom Hearts is probably the closest thing I have to a guilty pleasure in which I place heavy emphasis on the guilty part. I've played most of the series except the mobile titles and the $40 demo attached to the HD remaster of DDD that came out a few months back. At this point in time, I honestly feel nothing for the franchise and I'm probably one of the few people on this forum who doesn't give a trout about KHIII cause at this point, I'm pretty sure the conclusion to the Xehanort plotline would just leave me disappointed like DDD was. So I guess what I'm trying to say here is that this is the only Kingdom Heart game that is going to pop up on this list because it's the only one I still have overwhelmingly positive feelings for, whereas every other entry is a mixed bag.
KH1 was an amusing experiment that really surprised me, but the gameplay has aged terribly. KH2 had way better, if kind of more flash than substance gameplay, but the plot was awful past the prologue. 358/2 had a great if kind of long winded plot, with some cool gameplay ideas that were ruined by being put on a a system that couldn't handle it. Birth by Sleep had some great gameplay and introduced some awesome new characters to the series, but ultimately made me wish we didn't have to use Sora and Riku anymore, also this game re-introduced a bunch of silly ideas into the story I wish we could have avoided. DDD had some interesting gameplay (not as good as BbS though) and pretty much hammered the final nail in the coffin containing my interest in the plot and main cast. I can only say that Kingdom Hearts is a series with great ideas that are crippled with juvenile plot lines and hampered by having to stay kid friendly. In a lot of ways, it reminds me of Digimon which has a similar problem.
So with my confession out of the way and the only real negativity I'll say about the series in general, let's discuss why this game is here. Note: I have only ever played the GBA version, so everything after here largely concerns it and doesn't put into accoutn changes made in the PS2 Remake.
Chain of Memories begins right where KH1 left off with Sora, Donald and Goofy looking for Riku and King Mickey. Sora meets a strange man in a black robe who suggests they go to Castle Oblivion where Sora will find something important that he has forgotten. Castle Oblivion supposedly has the power to affect memories and Sora and the others have their abilities sealed into cards and the various floors become reflections of places within Sora's memories. The higher Sora climbs, the more he begins to forget, but he suddenly remembers a girl that was also on Destiny Island with him, Riku, and Kairi. A girl named Namine that Sora and Riku fought over. The plot heavily deals with the theme of memories and how they make us who we are. Being a kid friendly version of this idea (see Ghost in the Shell for the less family friendly version) Sora and everyone else will learn that even without memories, it won't change the kind of person you are deep down. Meanwhile, Riku is also a playable character in this game with his own story. Riku also finds himself lost in the castle, but unlike Sora, who is losing memories, Riku finds himself haunted by Ansem, Seeker of Darkness, who represents the darkness still in Riku's heart. Riku goes on a story of redemption and to overcome his guilt for all the bulltrout he pulled in the first game. Overall, the storyline of both characters deal with interesting existential crisis as Sora becomes more flustered and confused as his memories are manipulated; while Riku does some serious soul searching through his own chapters. It gives both characters some much needed character development which they will sadly never really get in the later entries as Riku kind of keeps forgetting the lessons he learned in this entry, while Sora moves from happy-go-lucky kid on an adventure of discovery, to KH's take on a Messianic figure, who is more important as a concept than as a person.
The plot officially introduces us to Organization XIII and the Nobodies, though the true nature of their existence wouldn't be elaborated upon until KH2. A shadowy organization who have plans for Sora. The group at Castle Oblivion are their to study the place, but it soon becomes apparent that there is dissent among the ranks, and a group of the newest recruits to the organization are secretly plotting to take over the organization. This ends creating a more interesting story than the simply tales of Sora and Riku, as we get learn more about the group and see the conflicting dynamics of the old guard versus the new guard. In fact, I still feel CoM did the best job of making the most out of Org. XIII as they ultimately get reduced to Mega Man bosses in the sequels, including the one that actually focuses on them, and ultimately get sidestepped as a minor threat when the later entries reveal the real big bad. In this entry, they are a real threat but also a conflicted unit where every member has their own motives and issues. Barring Axel, the surviving members in KH2 are mostly on the same page with Xemnes, and offer very little individuality beyond a personality quirk or two. Which is something I found rather disappointing after the more colorful cast of CoM.
Gameplay is kind of deceptive in this game. Most people know it as the "card battle game" but while cards are a major focus, this is not Magic: The Gathering, and the game is very much still an Action-RPG.There is just now more of a strategic element to everything. All actions beyond running require a card. There are five types of cards in battle: Red Cards which are action cards. They have various keyblades on them and allow Sora to swing them. Each Keyblade has various strengths and weaknesses and understanding how Sora naturally combos and placing the cards in an order that maximizes their efficiency is a large part of making a strong deck. Blue Cards are Magic and Summoning cards which work pretty much the same way as the first set, but I would like to stress that magic and summons are ultimately more useful in this game than the console titles. The 2D plane and smaller battle arenas make magic far more effective and the summons odd gimmicks are designed to work better than their odd mini-game/special command nonsense in the other entries. Green Cards are Item cards which help restore health and your deck. Black cards are enemy cards randomly dropped by enemies or gained from defeated bosses, and they offer a slew of really cool passive abilities like changing the number on your cards or boosting their effectiveness. The last set are technically the same as Blue cards, but are acquired differently and are temporary, and these are Friend Cards which randomly appear in battles and let you summon an ally like Donald and Goofy, or the world's corresponding hero.
All cards have a number between 0 and 9 and you can neutralize and enemy attack by playing a higher number card than theirs, or use a 0 card which neutralizes everything but can also be neutralized by any card higher than it. You can also build Sleights, which is where you combine three cards to fulfill the requirement for a special skill or to increase the potency of a move. Using three of the same magic card will raise its power from a simple Fire spell to Firaga, Freind cards will cast more powerful group hitting moves, and certain combinations will unlock Sora's special skills from KH1 like Ars Arcanum and Trinity Limit. Of course some of these combos require low numbered cards, so you'll have to think about that when building your deck.
This is ultimately what I really love about the game is building the deck to really customize how Sora plays. As he levels up, he can increase the size of his deck and you get more customization options. The game also has a versus mode which kind of counters the one gripe I have with the battle system, which is the dame gripe I have with many of the FF titles. There are loads of really cool customization options, but nothing really worth using it on. Yeah, you can build a deck that can finish off any boss in the game due to it's intricate and carefully planned layout, or you could just grind long enough to build a Cloud deck and Omnislash everything in the game. Sadly, the second style is actually easier to do and more common among people I've discussed this game with. At least the versus mode gives it more of a purpose, but good luck finding anyone who has the GBA version and the cable to do the head to head.
Riku's gameplay is slightly different, and frankly, I find his gameplay a bit more fun despite his general strategy for winning battles is ultimately the same in every situation: Build the right sleight to go into Dark Riku mode, spam Dark Aura, and win. What makes his gameplay more interesting is that Riku can't build a deck of his own. His deck is handed to him and he only has a few Sleights he can use. He's compensated by having ridiculously overpowered move set. Instead of increasing his deck size, Riku can increase his attack power and how long Dark Riku mode lasts, though increasing the time limit for the mode also increase how much more Riku has to do to enter the mode. Riku can gain enemy cards which he keeps through the various levels and this proves invaluable. The enemy cards are flavor stuff in Sora's game but are incredibly essential in Riku's game. Tjis is because Riku's deck actually get weaker the further you get in. His first deck in Hollow Bastion is filled with 8 and 9 cards, but his deck on Destiny Island is mostly 1-3. Riku's final boss is also more of a headache than Sora's, but Sora probably has the more difficult boss battle in his game simply due tot he fact that Sora's battle is one of attrition whereas Riku's take on the fight comes down to who can kill who faster. This brings up the fact that I find CoM to actually be one of the most balanced games in terms of difficulty in the series. It's not too hard, but it's not as easy as the other entries tend to be. There are some actual challenging boss battles in this game and your ability to grasp and utilize the battle mechanics will play a large part in how easy you make it through the game, whereas I often feel the other entries really comes down to just spamming attack peppered with an occasional healing spell or special attack to win most of the story mode, and the real challenge of the game comes down to the optional stuff, which I still consider to be an awful design Squenix can't seem to shake.
So yeah, a great game wrapped in a really thought provoking story that gave the impression the series was going to go into some deep territory with the overarching plot is what ultimately makes this entry stand out to me. For me, this entry was the last time I really had high expectations for the franchise before the later entries crashed me back down to reality and made me except the series for what it is: simple fun for a different audience than me.