Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
You know, I think that Kingdom Hearts is an excellent example of how movie studios and game studios -should- work together. Game studio makes the gameplay, movie studio provides the voice acting, plot comes from both, and the main character's especially created for the game... It's rather obvious that if you let each part of such co-operation focus on its strengths, the result can be a game suitable for many kinds of gamers. And thus, our new hero Sora enters the scene.
And his scene, Kingdom Hearts, is mostly enjoyable, if a bit tedious at times. The plot is pretty much everything you expect from a partnership of Disney/Square, but thankfully, gamers were kept in mind here, ensuring that while you can't avoid certain moral lessons, it's definitely not going too cuddly-cute for most. Nor are any of the main characters expected to drop out in a sing and dance routine, the only real song instead being one of the better j-pop tunes I've ever heard, performed in the intro movie. Cute, but not annoying, which is many steps above the norm in that genre.
Of course, it really helps plotwise if you're a Disney-fan. But it still works quite all right if you, like me, aren't (I'm mostly only into the Pixar stuff). But, I have an aversion to spoiling plots even indirectly if it's not something painfully obvious before you even buy the game (such as moral lessons), so, let's get over to gameplay instead.
The gameplay is sort of like Zelda with helpers, but without all the awesome different weapons and items, and with a good dash of Final Fantasy mixed into the background. What this means is that you'll basically be fighting enemies in real-time with your trusted keyblade and some magic. There's a fairly varied bunch of them, but apart from a few very cool bosses (Maleficent in her dragon form is, after all these years, still the Distilled Embodiness of Dragon, which means it's big, black, and scary), nothing that really stands out. But although it's mainly all about a sword, it's not only just swinging it, as you'll have to jump and avoid the stuff they throw at you. And some that requires a bit of timing, though you'll probably end up whacking your sword at them anyway until that spot opens up.
So far, it's been mostly action, but now the FF part kicks in: Every enemy you defeat earns you EXP, and EXP, naturally, earns you levels. Which again gives you both new abilities, and better stats, both of which makes a difference. Some of the abilities are critically important (Second Chance is literally a lifesaver on Expert difficulty), others are quickly forgotten. B ut most of them are useful to at least some degree, and since you have a limited amount of Ability Points to use, juggling which abilities you'll want to have in the upcoming battles can make you spend some time. You can easily just unchoose ability X and go for Y instead at any point.
Now, I've talked about the battles as if you're alone, and that's pretty much how you should approach it. However, you do have two companions in Donald and Goofy, and you'll also meet other characters you'll temporarily be able to have, but it's you who will do the main bulk. So, what are Donald and Goofy for? Well, two things: One, to draw enemy fire away from you. Which can definitely be a good thing, giving you a few more seconds to choose a certain spell or item. Secondly, once Donald has access to Cure magic, his main mission going to cure you. And as soon as they have their "Second Chance" abilitiy, you don't really have to worry about them ever again, because Donald will take care of anyone with critically low health.
In other words, while the AI isn't really that great, you can, by tweaking the settings, at least make Donald and Goofy reliable for the two simple tasks you need them to (plus, they'll usually make the battles go by at least a bit quicker). But, the only person that really matters whether keeps on living or not is you. Which means that whenever you find stat-enhancing items or accessories, Sora's always getting the best pick. Always.
Apart from combats and talking to people, there's also a fair bit of jumping, but getting to the places you need to go is mostly quite simple. Getting to places with interesting chests can be another matter entirely, and the camera, which can't really be controlled properly even on manual setting (and don't you dare thinking about leaving it on automatic), doesn't help in this regard. There are also some other minigamish things happening here and there, but it's almost impossible to fail if you simply go through them just to proceed in the game. Getting a good score in many of them is quite the different matter, though...
And so you go through different Disney worlds... Well, one more thing: To get to those worlds, you also need a Gummi Ship. And each time you go to a new world, you'll need to pilot the ship through a series of all the dangers you expect to find in space. Meteors, enemy spaceships, strangely shaped blocks, etc. It's possible to build and upgrade your ship very much.... But it takes time to even understand what you're really doing. Still, even if I eventually found some enjoyment here thanks to my obsessive-compulsive playing style, I can't guarantee the same for you.
The ordinary music's mostly quite nice, especially in the two last worlds (though I've always been a sucker for good classical-style scores in video games). One good thing is that the random battle music's different for each world, and of course more suited as well. Graphically, it's a clean and fairly simple style, designed for a cartoonish look much rather than "shiny" 3D. Mostly the Disney character's survived the translation to 3D very well because of this, although a few of them seem a bit strange. Oh well, definitely not a deal-breaker, unless you're so obsessed with Disney characters looking exactly like they did in the movie, at which point the problem is at your end.
Voice acting's mostly provided by Disney, which means we're getting a solid performance, if not actually all that impressive. Some of the characters you meet are talking a bit slow, but mostly not so bad it's annoying. Hades, on the other hand, is fast, slick, and generally done much too well for the small part he's getting in this game. I want more Hades!
So, all in all, it's a pretty decent action adventure game that amongst can serve as an easy gateway to understand the deal about console RPGs without starting with the heavy stuff at once. It also has the problem of repetitiveness, but if you can take that and mostly not-much-fun (but quickly done with) minigames, it's actually got quite a bit to stay for. And of course, it's always good (and rare) to see established movie characters in a good game, and this game's got more of those than you can shake a big key-shaped sword at.