I would have to say Johto. Why? Do I need a reason? Johto had some of the best Legends (Ho-oh and Lugia) and also that was where the greatest innovations of pokemon were made: Eggs, Genders, Friendship (Okay that was in Kanto too but it became important in johto) , Skarmbliss(lol), breeding, rematch trainers, different pokeballs for different situations, berries ; it all started in johto.
(Also, Hoenn and Sinnoh spelled wrong).