Yeah, I was thinking along the lines of 'don't forget' or 'don't overlook' the plot. This is a more detailed version:
Video games can be a story-telling medium, like films and novels, with some exceptions. Pokemon is not one of the exceptions. It's so easy to get caught up in spriting, mapping, and coding, probably because that's what comes to mind when making a video game. But with all the cool game play ideas, putting effort into a compelling plot and strong characterization is often forgotten.
You could come up with two hundred original fakemon, and throw in twenty new and intricate field effects for good measure; this might get the player through a couple episodes. But you can't bury a boring, cookie-cutter Pokemon plot and bland, uninspired characters under a mound of 'features'. After the dazzling glamour of your shiny new things has worn off, people will realize your game has nothing else to offer and walk away. What keeps even the most casual players (those who are frustrated by every gym) coming back to Reborn is because they can't leave the amazing story incomplete; let alone abandon the characters they've grown so fond of. Without it's plot, Reborn is just an infuriatingly hard Pokemon game with a lot of field effects.
The number one thing you are doing with a Pokemon game is telling a story. Good quality sprites and maps are essential features to have, don't get me wrong. But fakemon and even Reborn's infamous field effects are also just features. These things are supporting material used to enhance the story, not the driving reason for someone to play the game.
EDIT:
@Dobby
Oh, I completely understand that there is more to video games than just stories, and I agree with what you're saying. A lot of the best games have no plot; but they do have some gimmick, some interesting quirk that makes them good. But if you give a person a Pokemon game with the same old, "get the badges, beat the bad guys" formula, they're gonna get bored pretty quickly if you don't spice it up with some twist or unique feature (I was actually bored by the last couple of the official games for that reason, but YMMV). The reason I added that comment is because anyone looking at this page for advice isn't making just anything that qualifies as a video game, they're making a Pokemon game.