About ten years ago, there was this worldwide phenominon about fictional animals that fight each other in a fantasy-like setting, and a lot of people started playing it, and the same people were unable to put their Gameboys down. I was one of those people. Also included was a trading card game and a TV show (both of which are still running). Although its popularity isn't what it used to be (the fanbase is more loyal, on the other hand), the franchise is still going strong.... cards, TV show and all that other boring stuff, but that goes especially for the main series of games, which actually gained a popularity boost.
A year back, Diamond and Pearl decided to show their faces in the 'States (and they actually sold more copies than any of the previous games!), and now that people can connect to each other on Wi-Fi, Pokemon is better than ever now.
I would have stopped playing it if the feature to play online was absent, since I had nothing to do after I beat the game (no Action Replay means no having it easy at the Battle Tower, which was poinless without the Point Exchange thingy), but thanks to that, I'm still a fan of the series, even after almost a decade of playing what was essentially the same game... a game that I'm not extremely good at when playing against other people, at that.
Despite that, Pokemon is still fun to play, and in my head, it transformed from a fun game that challenged me to find and catch every Pokemon in the game to a slightly more frustrating strategy game where good movesets, stats, IVs, and EVs mean pretty much everything.
Sorry I made this post so drawn out... I just felt like writing something.