I found the PS2 games quite fun. The game's world is very entertaining, too. The GBA game, on the other hand, kind of weird. I didn't like its battle system and the worlds confused me - after playing Kingdom Hearts 1 and 2, Chain of Memories' world seems pretty limited. I don't know if playing Chain of Memories between the PS2 games would fill story gaps because honestly I don't pay attention to the story so it didn't matter much what I knew or didn't. I was having plenty of fun with the fast battle systems without worrying about story.