One of the things I hated about Ruby/Sapphire was that you couldn't legitimately fill your Pokedex, even if you lived in Japan. Yes, the giant data structure change was like rebuilding the entire game, and yes, Japan got the unlocks for the islands that had Deoxys, Lugia, et al, but there was no day/night function, so getting Umbreon was impossible- Contrary to the series mantra, you could not catch them all. And that's a big enough travesty.