Overall, I'm disappointed with Sun and Moon.
I didn't like X/Y because the mega evolutions weren't really additions to the dex, since they are really just glorified form changes. We didn't get as many new pokemon, and since gamefreak didn't give more of them useable stats to make up for it, there weren't very many new additions to competitive play compared to Black/White. If it weren't for the introduction of Fairy types, it would have been more noticeable and caused some stagnation.
Sun/Moon are the same. Instead of mega evolutions, we have what may as well be called "Uber Beasts", which are a stark and unnecessary change in tone. The Alolan forms are much preferred to mega evolutions, since they're "permanently distinct" and therefore are more effective as world-building components, plus they aren't abominations of gameplay balance, but there could have been more of them, and then some of them are missed opportunities and it would have been interesting if they were given more base stats/slightly different spreads, since that would bolster the theme of island biogeography resulting in rapid adaptation.
And again, we have a regional dex with a lot of really cool concepts that won't see competitive play and some that are going to be hard to justify using even in-game. I'm especially angry about Golisopod, and Aquaranid; one has decent stats and a crappy ability, the other has crappy stats, a questionable movepool, and an interesting but useless ability. The fruit princess is funny but her signature move is lackluster, Lurantis is in the same boat, almost. Kommo-o doesn't get Close Combat, which is absolutely baffling, Vikavolt isn't tanky enough or fast enough to do much, Palossand is basically special Golurk in the worst way possible, we got a really interesting pikaclone that doesn't evolve because, you know, Pikachu evolved and that /totally ruined/ Pikachu's marketability.
The thing that baffles me the most is that so many of the new pokemon are so slow. I'd actually really appreciate it if they just slowed down the game in general (gen VI would have done this, but it also introduced megas, which overshadowed things like sticky web), but introducing a generation of mostly-slower pokemon isn't going to fix that; people will just pick the few that are faster and the rest will be relegated to oblivion, because making the new pokemon slower doesn't mean the existing pokemon are slower and they just stand out more. The silver lining is the new distribution of useful moves and better stats to older pokemon, which makes up for some of the disappointment, but really doesn't do nearly enough and is poorly applied in some cases (Farfetch'd, Masquerain).
I'll just stick to Pokemon Showdown. I'd love to be proved wrong on these points, because I was excited for Sun and Moon at first, but I think a lot of the new pokemon will just never get the spotlight for any niche or team strategy and the boosts to older pokemon weren't enough.
