For X and X-2 I would say the HD Remasters are their definitive versions. Sure, some might say the remastered graphics and soundtrack on X are a little weird, but still. For X-2, there's no competition, at least not outside of Japan; the HD version is far superior to the original ^^ although if I really were to recommend it to someone I might actually tell them to stay clear of the new features up until NG+.

If anyone in my vicinity is interested in FF XII (and won't just emulate it) I will gladly lend them my PS2 and my game disk so they can play the IZJS version instead of the original.