>>37955758>tldr: i like it because of the memories and because it's comfySorry for wall of text.
Oh boy... What to talk about... First thing that comes to mind has to be the memories. I remember when i was around 7~10 me and my friend used to roleplay pokemon battles, he'd usually choose onix and i grovyle. It's kinda cringy now but we had a lot of fun back then, also, at the time we only knew about the pokemon anime, i've only heard there existed pokemon games when i was around 13/14, and that's when it all really started. I remeber telling to my other friend who was also into pokemon about the games (the one I first found out about was RSE) and we were really curious to find a way to play it. Later that year i've learned the way to emulate emerald on the computer and we were ecstatic, we couldn't trade or battle with our pokemon since we were only playing it in our homes but we'd spend most of the time just talking about it. It's probably because of these memories with the gen 3 games that Hoenn is my favourite region despite the fact that i really love big cities over small towns and if i'd pick nowadays without nostalgia blinding me I'd say Unova is my favourite region because of the nice comfy city filled with skyscrapers and changing seasons. Wich brings me to another reason why i love pokemon, the comfy environments. I remember the first time i saw the ashes of mt.chimney while playing emerald in the cold of winter or when i first realized the seasons were changing while I was leveling my pokemon in gen 5.
As a side note, i really dislike alola and can't bring myself to play the gen 7 games, not because of the mechanics or the characters, but just because the region means little to me. I love cold/temperate climates and hate tropical climates, the whole beach/hawaiian thing never appealed to me, so the whole reason i had for playing the other games isn't there, it's not comfy it's just a bunch of really hot/warm islands full of surfers.