I seriously don't understand all those who believe that XY is better than S&M. Both of them are disparate from each other; that is, they are so different from each other that they are beyond comparison.
Pokemon Sun and Moon is not a comedy, sci-fi, or adventure. It is a farce with a witty, carefree, and heartful aura around itself. Ash Ketchum is more childish in the series. But in no way does that diminish the most appealing element of Pokemon- battles. In other senses, he is pretty much the same. Sure he may not look like so, but he is as good a trainer as the XY Ash. Another great improvement in S&M is the rivals. For me, Gladion is much better a character than Alian from XY. In no way do I imply that Kiawe is worse.
Then there is the setting itself. Sun and Moon is set in the Alola region, a group of tropical islands. There are no Pokemon gyms here, but we have something even better. An avid lover of S&M needs no introduction to that. If you notice our protagonist's journey through Sinnoh, Unova, and Kalos, you would find many similarities. Such as these:
1) Ash's first catch is a Flying-type
2) He loses either his first or last Gym battle
3) His friends befriend more or less the same number of Pokemon
So over the seasons, the predictability of the story increases. Now, who would ever want that?
But everything has changed. Who can predict what will happen in the Pokemon School the next day, considering the novelness of the concept?
Give it a shot. The animation radiates a particular brightness, something not found in XY. It's not just a treat for the eyes, but all other senses as well.