>>202135891. Good diversity in the new 'dex.
2. Best online functionality ever... wonder trade took some time but is now fundamentally awesome.
3. Amie. Best trainer / pokemon interaction ever... yeah, it might get old after 5 minutes, but sometimes you just want to pat your gyrados and tell it it's been a good giant laser death fish. Plus: Those sweet, sweet bonus crits and status curing and hanging on at 1 hp... so good... so very good in single player.
4. Breeding: Both in terms of an easy egg-gatherng route, and an easy hatching circle.
5. horde battles: Hell, EV training in general got wayyy better.
6. Customization: it's the litte things. Even if they aren't equally balanced between male and female...
7. No goddamn pointless athletic / competition hall / fashion show / stop after the 2nd gym and do this unrelated thing which won't have any impact on the rest of the game... thing. Trainer videos didn't even need to be done.
8. Friend Safari that really, really encourages you to expand your friends list.