I still haven't finished a 4th gen game! But that's not because of the region, it's because of the slowness of the game sorta.
I loved the Hoenn games, but not because of the region. Imo Hoenn always felt a bit too modern and soulless to me, despite its story about Groudon and Kyogre and all. Sinnoh was different. Sinnoh feels genuine and deep with memorable areas and some kind of traditional greatness to it. Imo. Sort of like Johto has and Johto is my favorite region.
So Sinnoh is definitely good in my eyes, even though it isn't on top of the list.