Playing through Emerald again I really have to commend GF on making a whole new gen that largely fit in with and felt like natural extension of I and II in the first soft reboot. Gen V felt distinctly separate in a lot of its designs. Gen III definitely introduced a lot of stuff that has been flanderized in the recent additions (namely the overdesigned legendaries) but in the context of the game itself it worked very well.
This nigga for example could easily be from Johto and wouldn’t look out of place at all. You can really play through the game with a team of entirely Hoenn pokemon that feel like they belong which is lost IMO in V onwards