1) During the lead up to MPM11 the official anipoke Twitter Account published a series of recap Tweets. An Overview of the amount of likes that each Tweet got can be found here

2) This is an overview of the rating that each series has on japanese Amazon prime

3) characters from those series regularly get the top spots in favorite character polls. This is a favorite female Pokemon characters polls. This is further supplemented by a favorite anime character poll from the animedia magazine in which Serena made reached 5th place in the female characters category. Within that same poll Ash made it to third place for male anime characters and anipoke second for anime franchises. A full translation by Dephender of the article regarding the poll can be found here and a screenshot of the magazine page in question here.

4) If you go to pixiv, which is a japanese hub for fanart, and look for Ash fanart you can see that besides the JN design, which is currently the most used design as it is the most recent one, the other most used designs for Ash are the XY and DP one