Gah, this poll isn't multiple choice! O_o
I really like all the regions. Except for Fiore, Orre, and Hoenn.
Fiore and Orre were just plain boring, and in Hoenn you needed an HM slave for almost the whole freakin' game. It drove me up a wall. Also, I didn't think Hoenn was very fun to explore. Almost half of it was ocean, maybe more.
Johto would be better if it was in a different version. I wish it wasn't as nauseating...
It's still awesome, though. ^_^
But if I HAVE to pick a favorite, I guess it's Sinnoh. I thought it was the most fun to explore, not to mention a lot of the Pokemon were complete pwnage!
It's sad that Hoenn isn't appealing to me, because that's where I caught my Rayquaza. :3