6th Gen Best thing that X/Y introduced?

I LOVE SITTING ON BENCHES :D But seriously I think my favorite part is getting to have fabulous clothes and be able to actually pet my Pokemon in Pokemon Amie. :3

My favorite new things for X/Y are the Pokémon-Amie and Trainer Customization. I love being able to interact with Pokémon in the Amie, as well as the Berry minigame (don't really care for the other Amie minigames, though).
I also really like the idea of being able to change your player character's clothing during the game-too bad they decided not to carry this feature into OR/AS (I thought GameFreak could have implemented this feature into the Hoenn games rather easily, even if it were to be in a reduced form).

I think Pokemon-Amie was a pretty nifty innovation. It wasn't a massive gameplay shift, but it allowed for everything else to be more meaningful. You put time and effort into being genuinely affectionate towards your Pokemon, and some of the flavour text you get throughout the game, such as 'Pokemon and Trainer are breathing in perfect sync!' and 'Pokemon gathered all of its strength to break through the paralysis so Trainer wouldn't worry!' really helped with the immersion. Ontologically it's just a gimmick, but it really has added depth to every aspect of the game.

I do wish they still had Pokemon following you around in the overworld, though. That was amazing.

Character Customization was the best thing over :)

Super training : being able to easily train your pokemon is what I always wanted. Specially the possibility to clean the progress easier
Trainer customisation : Finally I feel that I AM the hero of the game. It had a higher dimension to the game

These are the 2 things that I really, really enjoy. That, and Greninja.

Ability to sit on benches?

XY introduced SO much material it's hard to pick just one. What really stands out the most to me though is character customization, mostly because that's been asked for for so long. PSS was actually a huge innovation too, because we no longer relied on Pokémon Centers for online gameplay which was a huge convenience.

- Character customization: Because dress-up! I hope it can be a feature again someday...

- Wonder Trade: So much fun to get random crap for your random crap! Trading without having to deal with people! Offloading your breeding rejects!! It's awesome.

- Easy IV Breeding via Destiny Knot: Am I the only one in this thread who's bred a million eggs this gen? And I don't even play competitively! It's just so easy, why NOT IV breed? 6IV Ditto not included in-game.

Amie/Super Training are pretty cool too but not in my Top 3.

Poke-amie, Destiny Knot and MegaEvo.

First of all customization. I'm the kind of person who still occasionally plays dress up with Barbie dolls, so this is absolutely down my alley. I also loved the fact that you could take photos at various scenic spots in 3D, makes the entire Pokemon experience feel more real (like you're really a tourist traveling through Kalos).

Loved Pokemon-Amie to bits and pieces of rainbows. I make it a point to max every single Pokemon I take into my team because I really want to have a fantastic bond with them, not just have 'friendship' increasing by bringing them around with me.

Friend Safari is great too. In previous games I might make the occasional friend to trade for Pokemon, but we just trade and that's it. With Friend Safari it gives me alot more incentive to check in on friends to see if they have beaten the game (to get the third Pokemon in the Safari), a bit like how Join Ave. in B2W2 made me alot more friends.

And something not mentioned yet so far - roller skating! Learning tricks and doing impromptu performances on the streets of Lumiose was so fun!

Mega-Evolution, for sure. We have many Pokémon out there that are generally underutilized in competitive scene, and this helps giving them a chance to get an upgrade, so to speak, and become more popular among battlers. Pokémon that don't precisely need a mega-form still do wind up getting one--those that are strong enough on their own--but I wouldn't say it's totally a bad thing, as it gives them an opportunity to shine even brighter than before.

The character customization, Wonder Trade, & Fennekin. I thought the character customization was pretty cool, but I didn't like the bag options for females or that you couldn't take male clothes and put them on the female and vice versa. Wonder Trade was just neat because you could trade whatever you wanted with whoever you wanted and what you got back was completely random. Fennekin's just one of my favorite Pokemon, so I'm glad that came along~

Character Customization- So many cute outfits to choose from, please keep this in all Pokemon games from now on Gamefreak.
Pokemon Amie- cutest thing ever! And it gives great bonus effects like evasion, critical hits, and more
The music- hands down the best in the series so far, it even has jazz, one of my favorite genres of music
Wonder trade- it is really fun, Today when I wondered traded and extra Archen with Pokerus, I was expecting a Bidoof but got an Asol instead, cool beans

Character customization, Super Training, and PSS, in that order. Character customization was a dream come true, while Super Training enabled you to have properly EV trained Pokemon on your main party and took the guesswork out of EV training teams for online battle. PSS made trading and online battling so much less of a hassle than the old method of having to be in a Pokemon center and needing to have the Pokemon you wanted to trade in your party.

I remember that I was so excited with the releasing of Pokémon X and Y because of the inovate things that these games introduced ^^ So my favourites features introduced are:

3D Graphics - I was so excited seeing all that 3D world, the 3D sprite and the 3D Pokémon! The graphics of Pokémon games have been growing and growing! For me, this is one of the things that I was more excited about!
Trainer Customization - OMG, I always wanted this! I always thought " why can't we change clothes to our sprite? It would be more realistic and there could be differences between players,etc" and when they released this in Pokémon X and Y I was soooooo excited! There are so many different outfits and hairstyles that can make your character different from the other player's characters and unique!
Fairy type - Always liked the new type! I was very excited for it! There are many people that didn't like the Fairy type, but this new type gave us many new strategies and moves for battle! Not to mention that most Fairy-type Pokémon are cute ^^
PSS - This made trade and battle online sooooooo much easy! It helps so much, one of the best features! I don't know what to say, it's just awesome!
Super Training - Really helps EV training, it's an awesome new feature, although I don't use it many times :/
Wonder Trade - This feature is funny! Trade one Pokémon for another, but you don't even know what the other Pokémon is xD It's a completely random Pokémon, it can be something bad or something really good!
Pokemon Amie - CUTEST. THING. EVER! It's an awesome way to increase the bond between the trainer and the Pokémon! It really helps in battle! More crits, evasion,etc! And I love giving food to my cute Meowstic *-*
Mega Evolution - It's an awesome new "form" of evolution! I was so hyped for Mega Evolution! It gives more power to different Pokémon! Awesome for competitive battle and normal battles! Most design are awesome and I love the fact that the Pokémon needs a certain stone, the Trainer needs a key stone and the two need to have a strong bond! AWESOME!
Roller skating - I LOOOOOOOOOOOOOVE Roller skating! You can learn tricks and roller skate in the streets! It's so awesome ^^

And there are other things that are really cool but I cannot remember right now!