I vote for Hoenn because it was easy to get an egg. All you had to do was deposit the couple Pokemon, then go out and go back and forth on the Mach Bike until the guy moved up front. Johto was great with the interaction, the hidden Super Potion, and especially the pond where you can get Staryu, but that is out-dated. As much as I love Four Island, the daycare has two flaws, one, that guy won't move to indicate that you have an egg, and two, the area is too small to accumilate enough steps effectively.
Hoenn would have been better in say Mossdeep, my favorite Hoenn city, but it is the best regardless.