This high review may be due to nostalgia goggles as this was a big part of my childhood, but man this game is awesome. There are a few flaws, but not enough to have a huge effect on the experience This review has no main story spoilers, but reveals a few post-game elements.
Gameplay: 9/10
The gameplay is very good actually. The battles are well-paced, and I like how you can customize certain aspects. For example, you can turn off move animations if you want to quickly go through a battle. Also, grinding is non-existent in this game whether you turn off exp share or not. this is a MASSIVE improvement to other games, as grinding sucks. My only issue with the gameplay is that the exp share is broken and leaves me overleveled. However, this is an easy fix, as when I play the game, I just turn it off when I am at around equal level to gym pokemon. Other great gameplay elements are the new pokemon amie and super training for their uniqueness.
Music: 8/10
Very good individual tracks, notably the clothing store and lumiose city music, as they were memorable for really giving the French feel to it. The reason this is an 8/10, though is that the battle themes aren't that good. I find myself forgetting about them and just listening to battle music from other games during battles.
Story: 6/10
The story isn't that good, but c'mon, it's pokemon. Nobody plays pokemon for the story. It had its good moments, but I felt it was very dumbed down to where it is like only meant for children, rather than having some hidden messages for older audiences.
Postgame: 8/10
The postgame is decent in my opinion, much better than people say about it. The looker quest is fun for some added story elements, and the PSS making competitive battling more accessible as you can challenge people any time and pokedex completion a lot more fun with the GTS, as you don't need every game in the franchise to transfer pokemon up. The battle chateau was the only mediocre part, as the difficulty curve wasn't that good. You start battling against first stage evolutions, which meant that the first 10 or so battles were boring sweeps. But then at around 12 battles or so, it becomes very difficult, and if you fail, you have to go back to defeating the low levels which took forever. I played the battle chateau for about an hour, then never went inside it again. Some minor touches that are worth mentioning are the various services in Lumiose and the character customizations that were fun to play around with.
Replayability: 10/10
Replayability is PHENOMENAL. I would give a 15/10 if I could. I have played this game more than I have played any other game before. There are millions of different possibilities of team combinations, which is the main reason why the replayability is great. I have played normal teams but different variations, monotype teams, stater solo runs, nuzlockes, dual type only with no repeated type runs, and many more. Playthroughs only last about 20 hours, so it only takes around a week or so to complete, making it a lot easier to just keep replaying and experimenting with different ideas.
Difficulty: 9/10
I don't understand why people always complain about the difficulty. Yeah its easy, but it is still a good enough challenge to make it enjoyable. You can also customize the difficulty culty by turning off exp share, playing on set mode (no switch-in opportunity after a KO), or adding extra rules like people do with nuzlockes if you want a little more challenge.
Overall a really good game. If you have a 3ds, it is a must-buy, but some slight issues set it back from warranting buying a new 3ds just for it