I guess most Pokémon fans think the Hoenn games (Ruby/Sapphire/Emerald or ORAS) are set roughly at the same time as the original Kanto games because of a deleted Matsumiya's tweet…
HOWEVER, in this line from Pokémon HeartGold/SoulSilver (set 3 years after the Kanto games), Steven reveals he is still the Champion of the Hoenn region.
This information should set the Hoenn games after the Johto games, since Steven is defeated by the protagonist of Ruby/Sapphire in the game's story, he couldn't have been the Champion of Hoenn at the time he speaks to the Johto protagonist.
I'm not exactly sure if I'm missing something, any opinions about it?
by let_victorinha