I've been a fan of the series since I was 7, maybe 8 or 8 at the oldest. I first rented KH1 from a Family Video and immediately fell in love with it, and later for my birthday my Mom bought the game for me. Saying I enjoyed KH1 would be a total understatement, I utterly adored it and still do to this day. The story, the characters, the graphics that hold up incredibly well, the music, there's so much to love. It was a revolutionary game for the time and a crossover no one expected so be so successful. It's funny to think about the ending to KH1, it was pretty risky in hindsight. Had the series not been a hit it would have ended on a cliffhanger forever and this would have been a niche/cult hit game ending on a cliffhanger.
I'll never forget seeing the ad on TV for Chain of Memories and hearing Simple and Clean play, it's all so nostalgic for me to re-watch on YouTube. Then of course going to Best Buy to get KH2 back on release day was an absolute treat, it's still my favorite game in the series and I know KH3 will surpass it! I own 358 too, and never experienced BBS, Coded or DDD until the PS4 remasters where I got to re-live everything all over again since the old days of the PS2 as well experience new games too. I almost never got back and play games on older consoles unless they are remasters, and since my PS2 and games have been sold off long ago the remasters make it all worth while!
As for reasons why I love this story, I'll break it into a few points:
Story: When it comes to the overall plot and various settings, KH goes above and beyond. A universe where Disney and Final Fantasy characters all mixed in one battling against the literal forces of Darkness? It sounds too silly at first and is a bit weird to explain to people but it just works perfectly I think. The Disney aspect is arguably the best selling point as it pays homage to classic Disney films new and old while providing great fan service and exploring worlds based on beloved Disney films offers a lot in creativity! Take away the Disney aspect and it would just be a generic JRPG story of Light vs Dark.
As for the storytelling itself it's a mixed bag, but it does get better as time goes on though I believe. KH1 was very simple and very cheesy but all the same it's very charming. CoM and KH2 added to the "darker tones" of the series as well telling better stories and each game setting up for bigger and better things. Sometimes the dialogue is a bit rough and the awkward pausing is noticeable but overall its very enjoyable, and the fact that the series and characters take everything so seriously makes it even better, it's entertaining and extremely creative overall for a game series and has a lot of heart put into it.
Characters: The wide array of characters in the series are also one of the biggest selling points, from the main protagonist Sora to supporting cast both original, Disney or FF all in one way or another have left big impressions on fans. Sora himself is like a lovable Shonen protagonist, he's an all-around good guy who just wants to help his friends. Riku I particularly like because you start off hating him since he's built up to be an antagonist, to being manipulated and eventually going on the path of redemption. And seeing them interact with Disney characters is also pretty fun, Donald and Goofy I especially adore for such good companions they've become to Sora, as well Mickey's wisdom and strength as he helps guide Riku to the Light and his attempts to help our heroes from the sides. Honestly this game got me into Final Fantasy, as I had never heard of the series before KH (granted I was very young) and the crew of Hollow Bastion and Cloud are all fun characters to see in the series. The main villains are also fascinating, especially Xehanort. Org 13 as well, they've always been my favorite villain organization for their impact on the series and varied, fun rouges gallery! Axel being the best one, and he himself is the most fascinating amongst the entire organization so seeing his redemption an true intentions were a fun twist I never saw coming.
Gameplay: The biggest selling point obviously to any game is the gameplay, and hot damn the main KH games are so satisfying! I've always been a big fan of action-adventure games as well hack n slash, and even then I'd say the main combat of KH2 I still find to be the best style of gameplay I've ever enjoyed. It's simple, fast paced melee combat with a neat magic mechanic thrown in. KH2 being the most wild as the game progresses and ability make you fly and slash all over the place at high speeds never ceases to entertain me. I see people who say they don't care for the story but thoroughly enjoy the gameplay. It's simply fun and satisfying.
Also to mention, the music is absolutely gorgeous to listen to and the vocal tracks from Utada are divine ~
So I may have dragged this out a bit but that was the best way I could summarize my love of the series, it's satisfying to play, has a great cast of characters with an entertaining story accompanied by a wonderful score, there's just so much to love and KH3 is shaping up to be the best in the series. We've never seen a game hyped as much as this one, so lets cherish this moment as its due to come out soon. Funny to think that I played the first game when I was no older than 7 or 8 and here I am 24 years old anticipating the final game in what we learned was the first saga in the series. I'm going to savor every moment of KH3, and hopefully it'll be a long time before KH4 comes out. It's a beloved franchise and thankfully this community is one of the better fanbases out there.