Gen VI is my favorite.
Okay, story time. I was the target demographic during the peak years of RBY, but my mother Strictly Forbade Pokemon anything because? Apparently it's virtual dog fighting?? So anyways, ALL MY FRIENDS played Pokemon and I wasn't allowed to do so, or watch the cartoons, or anything. It sucked, lemme tell ya.
So then years pass, and I'm in the middle of my teenage rebellion and I pick up Pokemon Platinum on a whim one day. And y'all, I was HOOKED. What I had intended to be a temporary distraction from my teenage angst turned into MY FAVORITE GAME. But by this point, none of my friends played any more, and I always felt a little...Well, a little late. I felt like Pokemon wasn't really for me, you know? Like I'd missed my chance to really play it. Like I really shouldn't like something that was clearly aimed at 10 year olds. So because of that, I always kept my Poke-love really private. I never joined any forums or told any of my friends.
So I play through Platinum and SoulSilver several dozen times. I thought it couldn't get better than SS and the Pokewalker. I was happy in my solitary experience, for the most part.
Then Gen V happened, and I hated it. The new mechanics threw me, and at this point a big part of the charm of Pokemon was the nostalgia for a game I hadn't been able to play as a kid. So the Only New Pokemon thing was REALLY offputting. So I didn't actually finish Black and never did get around to even trying Black 2.
I wasn't totally done with things, though. I kept replaying SoulSilver and eventually got copies of Leaf Green and Emerald and played those too. It was fun, if lonely.
And then XY hit, and it was magical. The games were dripping with the nostalgia I was chasing. So many nods to Gen I, to the anime, to all the things I had caught glimpses of as a kid and had finally seen for myself 15 years later. All the things that made me want to play in the first place.
And the new engine! 3D! It was beautiful, and it brought the game to life in a way that I couldn't even have imagined. I always said that one of the things I LIKED about Pokemon was the simple graphics, but man, 3D was worlds better. And trainer customization! Outfits I would legit wear IRL! A haircolor that was almost exactly like mine! THE ABILITY TO PET YOUR POKEMON HOLY CRAAAAAP! Not to mention the PSS! I wasn't alone anymore! I could find someone to battle without having to trawl forums and IRC and feel like a sad lonely lump with no friends! I didn't need friends who played! I HAD PASSERSBY!!!
And Kalos! It's so beautiful! The music is enchanting! I could stand around in Anistar City all day just listening to the theme music.
Basically, XY was everything I had ever wanted and wished for in a Pokemon game. Not only that, but the PSS and the marketing showed me that I wasn't alone in still liking the franchise as an adult. It was the first time I ever really engaged in the community, the first time I dipped my toes into competitive play...Sinnoh may be where I started my Pokemon journey, but I will always consider Kalos my "home region."