Favorite Things in Pokemon Games?

It's been ages since I last worked on my fangame, and I've been wondering what I want to work on while waiting on various plug-ins. To help with that, I want to ask, what are some things you like to see in Pokémon games? The it can be something from a game that's already out, an upcoming game, a fan game, or even something that nobody's done yet. For example, I like being able to visit multiple regions in a Pokémon game, and the only time that's been done in a mainline game outside of the SV DLC are the Gen 2 games and their remakes unless you count the Sevii islands as a region.

 

Not sure if I could add contests, which I kind of liked too, but this does make me want to revisit the Pokeathlon from HGSS.