Pokemon Ultra Sun and Ultra Moon are the best pokemon games of all time. They are also the last generation of pokemon games that will stay true to the motto of "Gotta catch 'em all!" as all pokemon from all generations can be played in these games, unlike the succeeding titles.
During their release in 2017, they received positive reviews and commercial success, becoming the ninth-best selling Nintendo 3DS games of all time. These games also have the best end game in the franchise, where you have to battle all the previous main villains of the earlier games, including their legendaries.
The Pokemon franchise is conservative in making changes, and it evolves rather slowly. Pokemon Ultra Sun and Ultra Moon are the culmination and epitome of this evolution and are among the best games ever made.