Pokemon Ruby was my first Pokemon game so of course I'm a bit biased, but Hoenn is by far my favorite region. I loved the story (despite people saying Magma/Aqua's goals were stupid) and I loved the geography a lot. There were just so many different environments to explore and I loved that it was half water half land. But the best thing about these games was their soundtrack, absolutely amazing. It is definitely my favorite video game soundtrack of all time, and honestly the music is a huge factor in how much I like a game.