It was a pretty decent concept, really. I tend to think the peak was with the release of Gold and Silver, those games were really quite good. I hated Ruby and Sapphire because you couldn't get ALL of the pokemon (I mean come on! It was on Gameboy Advance! You'd think they could make the world much bigger and have all the pokemon in it!)
I would still play the game if they revamped it and concentrated on what really made the game fun: the options. Tinker with party size, different pokemon, different paths (want to become a master? Breeder? Gym leader? Go for it!).
Really, I think the best thing they could do for Pokemon is make a massive world and place it online. Players can log on and challenge each other to matches and generally enjoy the concept in real time, and also be allowed to make their own gyms and the like. That would be a lot of fun and I'd definitely play. But really, they're just milking the same basic format, and it's getting laughable. It has a lot of potential, so much more can be done.