Why Kingdom Hearts is so successful

Hitting North America in
late March, Kingdom Hearts II managed to outsell all other games for the month after only a few days on store shelves. Game Daily asks how this spin off series become such a hit. From the article: "The critical reaction to Kingdom Hearts II has been just as positive as the commercial success. Most have praised the game for its high production values and expanded gameplay modes compared to the first game, giving it a 89% on GameRankings."

What do you think makes this hybrid Disney/Square game such a success?

[via Digg]