>>562049551. Despite having a small dex, majority of the Pokémon in it actually looked good and some even were competitively viable.
2. Good looking locations. I personally didn't like the exploration much, a lot of the routes were simple with few side areas, however they still had catchy music and interesting Pokémon variety.
3. PSS and other bottom screen features. The PSS was easy to use and looked cool. Super Training was fun and Amie was an interesting concept.
4. Exp Share functioning like Exp All from Gen 1. While it did often lead to overlevelling, you could always turn it off. Sad that later gens removed the option to turn it of.
5. While the overall story was pretty mediocre, I still enjoyed a lot of the characters, like Lysandre, Sycamore and AZ.
6. Some of the coolest Legendaries.
7. Mega Evolution is an interesting gimmick even if it was done a little poorly, I mean there's only like 4 mandatory battles that use it, I would have made the last few Gym Leaders and the E4 use it.
8. Battle Maison, while being one of the easiest facilities, has one of the best asthetics of any battle facility in the series.
My only big complaint was the brainless difficulty.