These aren't in any particular order since my feelings can change at any time, but these five are the Disney characters that have always stood out the most in Kingdom Hearts.
5. Ariel--Red haired mermaid from Atlanticia. In the first Kingdom Hearts, she is VERY useful as a companion since she is fast and powerful. Of course, it's expected that she be strong since the ocean is a harsh place. She's also adorably curious, spirited, and radically different from the "other" little Mermaid she was based on. Sure, she's from DISNEY, but still, the actual story is depressing.
4. Peter Pan--Flies, is powerful, useful, etc, etc, etc. Sure, he'll never grow up and tends to be on the simplistic side, but he's a well-rounded hero.
3. Mickey Mouse--I don't care much for the "King Mickey" thing, but he's been helpful in a lot of ways, ESPECIALLY in Chain of Memories. Had it not been for his card, I might not have been able to beat many of the CoM bosses. Now, if only his card would show up during the second Vexen fight...
2. Mini Mouse--DO NO UNDERESTIMATE HER. Her "faith" attack can wipe out any Heartless it goes near. Even though she doesn't appear much in the series, she's still quite a prominent character in her own right.
1. Goofy--Doi. Seems like he's dumb as dirt and yet has an awful lot of insight. I don't have to say anything about his prowess as one of Sora's "sidekicks".
And that's about it. I like some of the other Disney characters just fine, but they didn't stand out as much. I also don't count the Disney villains, but I'm kind of "meh" about Maleficient anyway.