Preferably one that’s not a rom hack, though I dig those too. I’m looking for something a bit harder than the originals and maybe a bit more mature, but still fair and whimsical. I’d like a game with pokemon from as many gens as possible, and fakemons are fine too.
I know you said you’re looking for something harder and more mature, but I cant help but recommend Pokémon Bushido, and Pokémon Xenoverse. Both excellent games imo.