[thinkingtoilet]

From what I've read, there is a massive amount of disappointment with the previous Pokemon games. I haven't played them but if you read about what the community thinks it's almost entirely negative. They feel like there is no effort put into making those games truly great. This game, apparently, is close enough to Pokemon to scratch the itch and is done well enough. That doesn't explain all the popularity but it explains some of it.