I have to say I really think they nailed the atmosphere in these games. With Castelia City, the abundance of different biomes and optional dungeons as well as the Pokemon World Tournament and other easter eggs, it feels like the most complete worldbuilding in any Pokemon game to date.
I mean just check this out:
https://www.youtube.com/watch?v=zj2N_SxWocQ. Entralink theme is GOAT tier too.