Hoenn is my all-time favorite region, because it had:
-Great Starters
-The best set of Pokemon
-The most varied areas (Volcano, hot springs, desert, ocean, forest, beach, underwater, abandoned ship, underwater cave, towers, caves, etc.)
-I liked the water, except for the Wingul and Tentacool, because you could explore it all, and find things like trainers and sunken ships afteryou beat the game as something to do.
-The best team (blank) plot, this was the only region where it was genuinely fun, because you weren't forced to fight everyone, and there were things you could skip, although you probably shouldn't, like the master ball.
-It had things you could almost describe as "side-quests", fun to do, rewarded, but by no means necessary. Like the abandoned ship, New Mauvile, The Winstrate family, and the Trick Master, Those are some of the funnest things to do in those games.
-The routes that served no purpose in terms of story progression, were fun to go to, and let you train and catch rare Pokemon, like route 115, north of Rustboro, or route 123, south of Mt.Pyre.
-Unlike the other games, which are somewhat boring at the start, the beginning of Hoenn is memorable in a way that makes it very fun, and sentimental in a way for me, as Ruby was my first game.
I really liked this region, And I don't really have anything bad to say about it, except they should have made Stadium 3 instead of Colosseum, 'cause Stadium 1 and 2 were great games, and Colosseum wasn't, except that you could use it to get starters from Jhoto.