After my first play through, I thought gen 7 was the best generation to date. I loved the story, Ioved the pokemon, I loved the graphics, and I've never been happier in a pokemon game then when I beat that shit eating grin off Hau or insulted him. It was amazing. Then I played it again, and I lost a lot of the luster. The story started to get tedious, Hau wasn't nearly as satisfing to beat because I got used to it, and over all I felt pretty drained out by the end of it. That's where I think gen 7 falls, it lacks replayability. I can't tell you how many times I've played gen 1-6 games, and I'm still excited to replay them with a stupid gimmick added in, but I don't want to touch Sun for quite a while because it's became a drain to play
On the bright side, it makes breeding for IVs and training EVs super easy, so that's a plus I guess