I was allllll about Kingdom Hearts back in Jr. high! Haha!
I definitely think Birth By Sleep is the best in the series, followed closely by the first game.
I have played all the games up to date. My favorites by far are Kingdom Hearts II and Kingdom Hearts Birth by Sleep. I cannot wait for three to come out.
I stopped liking it nearly as much when Dream Drop Distance decided to make Master Xehanort a blatant Villain Sue at the expense of any senses of accomplishment from all the previous games.
I got kh1, kh2, kh chain of memories, kh 358/2 days, birth by sleep, kh re:coded (its not rly that impressive), and kh 3d... ad saving up for a ps4 to get kh3