I love XY for a variety of reasons.
First of all, I love the layout of the region, I admire the French and European feel and a lot of the city designs are stunning. Anistar city is gorgeous, Laverre city is unique, etc. However, Lumiose city stands out the most, I appreciate it's design being based on the lovely, romantic city of Paris, and I love it's gargantuan size and all that there is to do in the city. A lot of the routes are very detailed and beautiful, such as Brun Way. The Pokemon Gyms were also very unique and heavily detailed which I absolutely adore as well. I think the design of the region alone makes it stand out a lot compared to other regions with more bland, simplistic layouts (aka Kanto and Johto).
The soundtrack is excellent. Maybe not as good in DP, but good nonetheless.
Some of Pokemon introduced had great designs, although there were far too few new pokemon which was a disappointing. Mega evolution is a fabulous idea, and I really liked its tie into the storyline, I also loved the introduction of Fairy types, and all of the numerous new Fairy types.
It's not totally perfect though, a lot of the characters were quite bland and didn't leave much of a lasting impression. Tierno's character seemed a little random, Shauna is cute and I like her, but she lacks depth. Calem is decent, he's rather boring and lacks any backstory as all he cares about is battling the protagonist, which gets a little repetitive, even annoying at times. He's also too easy to beat, I just feel like he's lacking, he's not a rival that really excites me in any way, shape, or form. Lastly, Trevor is sweet, but again, he has absolutely no depth.
Team Flare is quite forgettable, I'm not even sure what their goals are other than the fact that they intended to wipe out all non-members of their ridiculously dressed group? Lysandre was interesting, but lacked the cool designs that Cyrus, Ghetsis, and N had. His goals weren't clear to me and there wasn't enough storyline involving him or his followers to allow me to fully grasp his desires.
Not all of the characters were dull, Professor Sycamore was phenomenal in my opinion. I love his constant involvement in the storyline, and his youthful spirit and vitality. He genuinely cares for his pupils and I think he was executed really well. I also quite like Diantha, she is significantly less involved in the story, but I just love her design and the concept of her being a high-regared, famed actress. Also, girl power!
The storyline itself is good, a bit more enticing than Black and White, it may have overall lackluster characters but the design is superb and the game itself was very enjoyable. The anime, in particular, was a HUGE recovery from the poorly executed and laughable Best Wishes Series.
