Hoenn, hands down. It had everything Kanto tried to have, everything the Orange Islands forgot, everything Johto lacked, and then some. Plus, it had some of the most hilarious episodes in history. Watch, "Sealed the Huge Claydol," and tell me there's a funnier episode in any of the previous seasons. Plus, some episodes manage to be funny and sweet. 'True Blue Swablu' comes to mind here. Ash is an idiot there, and hilariously so, Torchic is a riot for once, while May gets some serious character development. Kanto has yet to pull that off, as far as I know(unless the banned episodes do this, in which case, I wouldn't know).
SC~ out