chain of memories is a really interesting game conceptually; it was made as a fairly direct gap-filler to lead into KH2, but it also was in response to demand for a portable version of kh1, and it wanted to make a good explanation in-universe for why progression gets reset from KH1 to KH2. ignoring the fact that the last bit is a very funny reason to make an entire game, this mish-mash of goals creates a very odd playing experience. i felt that the focus in the story on jumbled and distorted memories created a fairly strong justification for the repeated worlds and bosses from KH1, while still recontextualizing those moments in a more interesting way. the semi-randomized dungeon crawler elements are also a really cool way to represent the fickle nature of memory through gameplay, and it's very fun to get limited customization of the room layouts depending on the situation. unfortunately, the focus on memories also extends to the combat system, which is very messy and definitely needed a lot of tuning. contrary to what many people say, i don't actually think splitting actions into cards is the problem here (reverse/rebirth proves this, imo). the bigger issue is the deckbuilding, which feels totally at odds with RPG progression and makes COM oscillate wildly between completely trivial combat and absurdly difficult combat. i tend to be a fan of experimental and "imbalanced" progression systems (the junction system in ff8 is a favorite), but COM's cards feel poorly accounted for; the game offers you relatively few guaranteed cards, and those it gives you are likely going to be pretty far from the cornerstones of your deck. this ends up meaning the boss design needs to account for too many potential playstyles, so you get lots of inflated health bars and lots of bosses that are designed around playing defensively and waiting until they have no chance to counterattack. i think it's actually very charming and cool that many of the bosses play by the same ruleset the player does, but because COM has no idea what cards you have, the only real surefire strategy against many bosses is waiting for them to waste their cards on sleights and catching them reloading over and over. if the progression was not as reliant on lucky pulls from packs, these bosses would be able to have more reliable and interesting counterplay, but unfortunately the systems here just don't allow for that. these incredibly boring and drawn out encounters are most noticeable with the final boss of the main game, where the most reliable strategy i could find was just to parry every attack he throws out with a 0 card, then use the cloud summon to chip at him a few times, repeat repeat repeat. this took about 10 minutes, and might be the most boring boss fight i've ever played.
reverse/rebirth fixes basically all of the issues i mentioned above by just giving you set decks for each floor, which makes most of the fights far more interesting. wayyy faster and less reliant on cheese, i love the emphasis on card dueling.
the story in COM is actually really great by the way. i could personally tell it was written after KH2, but it's still a pretty interesting story that explores the inner psychology of both the protagonists a little bit. there's a lot of cool hints at future games (i think, at least) and the addition of organization 13 is just great. i had found the overemphasis on disney elements in the story of kh1 to be a bit frustrating, so COM's story was a great change of pace.