Needs a different story line - I'm not going to bother buying any more pokemon games if they involve some boy or girl from a small town on a quest to defeat gym members, defeat a cult or crime squad on the way and become the best trainer. Come on, mix it up a little bit. Pokemon games are more formulaic as hell, I know what's going to happen before it happends. You'll find the same HM moves, battle with a rival, get the Flying move about halfway through, there'll be a cave puzzle somewhere along the line and they'll be a few legendary pokemons about, you'll get one masterball...... yawn. After two games that were pretty much the exact same thing I lost interest.
Oh and one more stereotypical pokemon thing: You'll eventually have to embark on a Road of the victorious sort, battling the same goddamn trainer types along the entire way.
If I can predict the exact plot, mechanics and events in a game, I'm not going to buy it. The Pokemon games, while fun, aren't varied enough to warrant me coming back for the same thing, except instead of a fire lizard you get a fire monkey.
CHANGE IT UP! Instead of fire, water or grass, give us, I dunno, Nuclear, Chemical or Biological starter pokemon. Make the villian the leader of the world, and you have to go to the various gyms and KILL the leaders and cement yourself as the leader. Introduce elements of real danger, and for god's sake make a world that doesn't revolve SOLEY around pokemon, a world in which every single bloody person only talks about pokemon every goddman day of their lives!
Pokemon also needs a technological upgrade. I know people like playing it on a portable system, but please, Nintendo, make you portable systems more powerful so that each new pokemon game DOESN'T look like just a slight graphical upgrade.
And stop with the nonsense of "only some creatures are on this cartridge, and only some are on this cartridge"! I hate that! I fell for your money-grabbing scheme when I was 10, I'm not that stupid anymore!
So:
1) Give us a world and a plot I can't predict in my sleep
2) Allow us the ability to get all pokemon without having to trade with others or attend those bloody "special events"
3) Change the art style! Don't just improve it.