Kingdom Hearts is a crown achievement in story-telling from two polar opposites.
In Kingdom Hearts, you play as 14-year old Sora, a resident of Destiny Islands who, after an invasion of Heartless, becomes a Keyblade Master and must save multiple worlds from destruction. Among these multiple worlds, you'll cross paths against the likes of Hades, Jafar, and Oogie Boogie, from some of the Disney properties.
The gameplay in Kingdom Hearts is not that of a very expansive or elaborate RPG, but the basic elements are there. Each character in your up to 3-man party has slots for equipment, and items to be held. Each character is also given Ability Points to pick and choose which abilities are activated and can be used. There is magic in the game, but it's not a very good system. You can shortcut 3 spells before a battle, but if you want to use a different spell, you'll have to scroll while dodging any enemies to do so.
Speaking of combat, it's my biggest gripe about Kingdom Hearts. Save for moving around to dodge attacks, it ends up being a button mashing fest. Worse yet: it's only one button.
Graphically, the game excels in every way. Wether it's an in-engine cinematic, or just the effects from the various attacks coming your way, the game looks beautiful in every aspect.
Sound is massive, there's a bunch of voice acting in the game, done by some names that may surprise you (Haley Joel Osment, Hayden Penetierre of Heroes fame and Lance Bass among them). All music in the game is also done by a full orchestra, and features two versions of the song "Simple and Clean" by Utada Hikaru. It may not be the most spectacular or memorable score, but it accompanies the game well.
Kingdom Hearts is not meant to be a Final Fantasy veteran's next big challenge, it's simpler than that, but it is a game that shows a remarkable story with familiar characters and new ones in tow.