I like the Hoenn climate, it's much more tropical then Johto's. I also like the huge amount of water you can explore. Maybe I like Hoenn better because when I played sapphire for the first time, I seriously did't know all the third gen pokemon, it was a huge adventure to me. I liked the secret bases, the evil teams' hideouts and the desert. Johto actually comes in as a third, behind Kanto, because it's way to linear. I like Kanto because you could travel to all cities with ease without the help of fly.
EDIT: whoa whoa , didn't notice this thread had recived a serious bump, sorry guysXD