>>35079709Bigger map, bigger cities, more locations of interest.
Make Team Rocket more interesting and have a bigger presence; more operations, more locations, give them the admins from Gen 2. Make it feel like they actually control parts of the region.
Add the opposite player character as a second rival, and change Blue's personality just slightly so he's a bit less of an outright dick and more of your friend. Make it so that both rivals are childhood friends of you and each other, and make them a boisterous bantering duo of friends instead of the "we worship the very ground you walk on" type of friends of later gens. Make it so that certain events can change who becomes Champion and who must fight you at the end.
Make pre-existing characters such as the Gym Leaders more interesting, and have them interact with each other more.
Perhaps add some of the good stuff from the anime.