With amazing story, great replay value, and fantastic soundtrack, Kingdom Hearts is truly a masterpiece.
The story is that 3 friends, Sora, Riku and Kairi, grow bored of their small world which only consists of 2 islands and set out to build a raft and adventure to other worlds far from their own. Meanwhile at a distant world, King Mickey Mouse has left to investigate the sudden growth of darkness and leaves a note for his magician Donald and captain of his royal knights Goofy. Donald and Goofy then set out to find a man named Leon in hopes that he can help them find their king. However, on the night that Sora, Riku, Kairi planned to leave, their world is engulfed by darkness and they are all separated. Sora lands in a strange world called Traverse Town and finds out that many other worlds have been engulfed by darkness as and surviving worlds have been overthrown by dark creatures call the Heartless. Sora then finds Donald and Goofy and joins them in a search for Riku, Kairi and King Mickey across many worlds.
The gameplay makes you mostly explore worlds, fight enemies and solve puzzles. A pretty basic mechanic but the game handles it very well. The fighting is mostly "hack-and-slash" combat where you hit enemies and then flee for a few seconds to heal yourself. However you can equip various abilities to prolong your combo and have more powerful combo finishers. You can also use various magic spells and summon allies to help you fight. The puzzles are also very well thought of and feel worth solving. Most of the worlds are made from classic Disney movies and are brilliantly created and feel like you've been sucked into the movies themselves.
Even after you've beaten the game you still have to fully level up, beat secret bosses, synthesize secret weapons and items, complete challenges in the Olympus Colliseum and collect special items from enemies in return for even more secret weapons. So yeah, there's a lot of replay value in this game.
To end this review, this game is simply a masterpiece and combines the worlds of Disney and Final Fantasy perfectly with beutiful worlds, fantastic soundtrack, great combat and engaging story.