They used to be good. The games had a good enough battle mechanic to have a competitive scene, and they had enough content after the main game to keep playing i

They used to be good. The games had a good enough battle mechanic to have a competitive scene, and they had enough content after the main game to keep playing it for a long time. The battles are simple, but can actually get quite strategically high level with lots of nuances if both sides know what they're doing. That kind of battling didn't come into play in the main game except maybe in the Elite Four, but it mattered afterward in the Battle Tower (or whatever it was called), and online battles. Also, you could transfer ANY pokemon from ANY game to the new game, complete with special moves and items, such as mega-evolutions. Building good teams and all the work going into it, from breeding to training, was fun. There were complex breeding mechanics to get pokemon with unusual moves or better than average stats, and there were side games like Pokemon beauty pageants that you could breed and train them for. Also there were extremely rare "shiny" Pokemon with unusual colors or markings. Those are still there, but it's a lot less meaningful to have one when you can't transfer it to other games anymore.