Hoenn is the only region that feels like a real adventure

>Kanto and Johto feel like roadtrips through the countryside
>Sinnoh is one big hiking trip
>Unova, Kalos, Alola and Galar are theme park regions

Meanwhile Hoenn is the most tropical, foreign region, with a perfectly designed map allowing you to find new areas whenever you have to backtrack. The new Pokémon fit in aesthetically with the strange locations and habitats you're visiting, which all feel dangerous and difficult to traverse. Uncovering the Regi puzzle feels like some Indiana Jones type shit as well.

Sevii Islands also has a similar feel but it's a small part of FRLG.