Oy... So much to reply to, lemme see what I can do.
1 Kingdom Hearts fan myself as well. Never played them, but I absolutely love the concept and would love to witness/experience someone playing the game from the beginning to the end.
2 The Heartless aren't rully the main bad guys, they're more sort of minions. Main minions.
*In Kingdom Hearts 2, they were bolstered by the addition of the Nobodies.
3 KH has a rich storyline... In the first game, you get to fight against the various villains from the Disney franchises. The Anselm Reports give you the overarching background of the story itself.
4 The main point is to defeat the Heartless, seal off the portal to each different world, win the keychain that seals the portal and adds to your Keyblade weapon, then go toe to toe with Maleficent as you save the seven princesses, and finally beat Anselm. However, the game doesn't end there...
5 There are three KH games currently out: Kingdom Hearts 1, 1.5 titled Chain of Memories, and KH2.
6 It turns out that the Anselm you fought against at the end of the first game was the leader of a group of thirteen main upper echelon baddies, called the Order XIII (Roman numeral for 13). You defeat some of these in Chain of Memories and others in KH2.
7 Chain of Memories connects with the other two main games, in that you have to fight through a total of thirteen realms all stacked atop each other inside the structure of Castle Oblivion.
8 From Castle Oblivion you then connect with the storyline of KH 2.
9 The selling point for KH2, the world I absolutely thrilled to learn about being included, was the Tron level.
10 The Muppet realm would be great, but I have other realms I'd like to see in KH3 and something else for Muppets I could expound on later.
Gotta jet.