Kingdom Hearts 1 certainly turned into a Disney/Final Fantasy fans' dream, and managed to sell millions worldwide.
The game then spawned two sequels; Kingdom Hearts: Chain of Memories was a Game Boy Advance game. For this reason alone it sold less copies than the other two games in the series – the Kingdom Hearts fanbase lies mostly with Sony's Playstation 2, and they weren't about to buy a Nintendo console for a single game. Despite its lacklustre sales, Chain of Memories was an interesting addition to the series, and was very fun to play. Most importantly, it was different. It featured a battle system that was a refreshing change from the 'tap x to win' system in the PS2 games.