>God Tier
BW2 Unova/Hoenn
Both are so much fun to explore. I love Hoenn because of its diversity of scenarios and the different ways you can explore, aside from the fact that it has the best Pokémon of the series. BW2 Unova has a great habitat list as well, and while it is somewhat linear, I feel like each city and route gave you a lot to explore and find, Unova hides tons of cool little secrets. But most of all, I think I like the seasonal aesthetic and the Unova culture. I feel like the games made me understand how Unova society came to be and it makes me feel like the game itself is more alive and immersive because of that.
>Good Tier
Sinnoh
BW Unova
I like the lore and a lot of the places in Sinnoh. For the most part, I also really like the exploration, although I do feel the game design prevents that from being as enjoyable as the best 2 regions. Also, I just don't like the Pokémon distribution. Despite that, I feel like Sinnoh is a complete region. And for the most part, I feel the same about original BW Unova.
>Okay Tier
Johto
Kanto
Kalos
Basically regions that I feel like they are incomplete or not as engaging or charming as the others. I feel like they have their own potential, but they could be much, much better. (Though I will say, Johto and Kanto benefit a lot from forming one huge region in GSC and HGSS, when they are together, I feel like they are almost complete, if not for how empty Kanto feels at times)
>Shit Tier
Alola
The idea was really good, but I feel like it was badly implemented in 3D. Areas are super short and exploration never feels much rewarding. Pokémon distribution is good though. I just really, really hate the areas and how empty they feel in SM.