>>51956962OP, I respect that you tried really hard with that statement. Made me chuckle
But to answer your question, really depends on the situation. Most of the time, the most popular Pokegirls are going to be the ones who have a presence. Player characters, anime protagonists, or pivotal in the game somehow.
Ladies that don't fulfill those conditions are often a mix of other things, but often it just comes down to how hot/cute are they, and do they permeate just enough into the public to stick around? Elesa and Skyla have remained perennial favorites for being hot, but also have the fandom uplift for being "Sappho and her friend" level shit. Gen VII tapped into lolishit with a trifecta of characters that everyone fawned over for one reason or another. Really just depends in the end, but it goes to show you can never predict who will be the most popular each gen in the end.