Squeenix's PS2 games tend to have better versions in Japan. These are the "Final Mix" for Kingdom Hearts, or the "International Edition" for FFX and FFX-2.
FFX differences: http://www.gamefaqs.com/console/ps2/file/197344/41079
FFX-2: not linked to avoid spoilers. You miss EPIC boss fights, and get a crappier music video.
Kingdom Hearts 2: http://wiki.answers.com/Q/What_is_the_difference_between_KH2_and_KH2_Final_Mix
If your PS2 can play Japanese games, I HIGHLY advise that you get the international editions, as there's no good reason to avoid extra content. Especially in KH2's case, as KH2 Final Mix comes WITH Re: Chain of Memories on the disc. The standard FFX is also ridiculously easy if you get the super weapons -- the extra bosses would give them a purpose that's not instant-win.
EDIT: Forgot to mention that all of the "International" versions can be set to full English, both text and voice acting.