I bought 1.5 collectors edition, then 2.5 didn't really come in a art case and it looked weird, so I gave my friend the 1.5 collectors as he's a MAJOR KH fan (And he was supposed to get collectors, but didn't as gamestop messed up)
I never played KH 1 so this was my first real chance too. I loved KH2 and birth by sleep so I did KH1 on normal... As it turns out, it's the hardest in the series people say... And it was a tough ride. Then after level grinding I determined that the game is all the same no matter what difficulty. Normal didn't feel harder, I just felt under powered until I got an appropriate weapon. And that's also why I don't like RPG's most the time.
Regardless, I beat KH1, watched the cinimatics, and not gonna touch chain of memories XD
For 2.5... I waited a looooooong time for that one. But, I haven't played them yet XD They are fairly long games, and I beat both the games anyway back on PS2/PSP, so I am good waiting for now ^^