The Characters - The recurring characters in Sun/Moon are better than XY's at least. Prof. Kukui is more involved with your journey than most other professors and Team Skull is probably the most entertaining team yet.
The Graphics - With no more chibi-models, tile-based overworld, or battle circles, the region feels a lot more immersive and so do the battles. I enjoyed all the little details in the environment and especially the new animations for some of the attacks. And Z-moves are especially impressive.
The Difficulty - The Totem battles in the beginning and middle of the game are actually quite a challenge compared to Gym battles from the past few generations. Important trainers also have fully EV-trained Pokemon for the first time ever.
The EXP. Curve - The game gives you an EXP Share near the beginning. Unlike XY where you'll be overleveled if you turn keep it on and underleveled if you turn it off, Sun/Moon uses Gen 5's experience system so high level Pokemon will gain less exp than low level Pokemon when battling the same opponent. This means you'll be pretty evenly matched with your opponents by the time you reach the end.
The Music - It's really good for the most part. My favorite songs include the Team Skull battle theme and two other battle themes, but they're spoilers so I can't actually mention them.
The Not so Good
Small Pokedex - If you exclude the Ultra Beasts and the Alolan Forms, the number of Pokemon introduced in Gen 7 is barely bigger than Gen 6. This is mostly due large number of single-stage Pokemon.
Gen 7 Encounter Rate - You're more likely to encounter Pokemon from older generations than Pokemon from Gen 7. Some of the new Pokemon also happen to be ridiculously hard to find and others can't evolve until almost the end of the game.
Too many cutscenes - The games have more cutscenes than any other game in the series, and your ability to go off and explore new areas is limited until you reach the next cutscene to advance the story.
Framerate Drop - Anytime there are more than 4 characters (Pokemon and trainers) on the screen at the same time, the game lags and the framerate just plummets. That means tag battles and Battle Royals will have your system experiencing a noticeable slowdown.
Overall, Sun/Moon are really solid first entries of a generation, despite some issues.
How are you enjoying these games so far?