>>41674660Cuz charizard was a shitmon for 5 gens in a row until megas made him usable for 2 gens. Only for swsh to cut megas out altogether and make him a shitmon again. His massive popularity is wholly unearned.
Gengar was OU for 5 gens until his mega made him Uber for 2 gens. Gmax Gengar isn't as good as his mega, but smogon discussions suggest that he'll still be OU in this gen. It's hard for people not to like a badass ghost that's also viable in competitive battles too. Well-earned popularity.