In my own opinion, I believe Final Fantasy RULES ALL. But apparently not the public. I loved Kingdom Hearts II and Kingdom Hearts Birth By Sleep, but not the first one, nor Chain of Memories (Is it hard to believe I'm still on the first level? I can't even unlock the first door!) But in overall, Final Fantasy has a pretty in-depth story with intriguing characters and a very well done environment. Final Fantasy X and Final Fantasy X-2 were in my top collection, the puzzles boggled my mind, and the interaction was sweet, the battling scenes were to die for, although the graphics weren't all too real in the game itself, the cutscenes made me weep. Final Fantasy (I've owned about 9 so far, and I want to expand my collection of how awesome it is.) However, Kingdom Hearts was my first ever RPG Game, the first thatI've ever played, and it lured me in and I was addicted. Finally, since Kingdom hearts includes some of the well-known and somewhat loved characters from Final Fantasy, it's quite a revolution that Square Enix created both of these lovable series.
In conclusion, I love 'em both to death. I dream of owning all the Final Fantasy games to date, and keeping my own collection of Kingdom hearts games and maybe in the near future.... figurines!