One thing which really needs improvement in Pokémon games is the story. I feel there could be something interesting done with the games instead of going "You're a kid, here's the world, go collect all the gym badges." Some of the games briefly talk about the mysteries of Pokémon and their origins, and I think a story centered around studying Pokémon and learning their secrets could be nice.
Also, EV training is one reason that Pokémon is truly a game for everyone. You can play it casually, collecting and training only the Pokémon you want with which to beat the game, or you can learn all about the stats and rigorously raise your team to max levels. It's up to the player whether Pokémon is "casual" or "hardcore."