One of my biggest disappointment is that it was way too easy. I never once felt challenged at this point, and I know it's targeted at younger kids, but even my 10 year old brother had no challenges at all beating this game. What age could they be aiming for if not for 10 year olds? (sidenote: my brother isn't very good @ puzzles). Even finding all the Pokemon was pretty easy, I mean, I haven't even beat the game and I already know where I can probably find Mewtwo and Zygarde. And it doesn't seem like it'll be much of a challenge actually getting them (aka RBY Rayquaza and Giratina) since my brother was able to do that pretty quickly.
Okay, fine, I guess I have another disappointment. There's only 60-something new Pokemon? Mega Evolutions were great and all, but I only like a handful of them, and only a handful of Kalos Pokemon in general (no, I'm not a new gen hater, I hate plenty of other old Pokemon too) and I'm kinda sad that they took the place of new designs. Especially because you can't even get all of the stones before beating the Elite Four, and you only get 1, so it's no fun to trade them around.
Ah, ok, finally, there is nothing to do postgame. I mean, catch all the Pokemon, I guess, but the story required you to travel the whole region, so then, there's nothing left. I did actually like how the story was different than BW's fight a gym, cross a bridge and battle zero trainers, then fight another gym approach to a "storyline."
There were a lot of things I really liked about this game, but there were just a few major things that I didn't.