Gen 8: Game Freak finally uses the Quartz trademark Nintendo have been sitting on years*. 18 versions of the same game, named after 18 varieties of quartz:

Pokémon Herkimer Diamond <-- Not a Diamond remake
Pokémon Rock Crystal <-- Not a Crystal remake
Pokémon Amethyst
Pokémon Ametrine
Pokémon Rose Quartz
Pokémon Chalcedony
Pokémon Carnelian
Pokémon Aventurine
Pokémon Agate <-- Does not contain Agate Village
Pokémon Onyx <-- Onix is not the mascot
Pokémon Jasper
Pokémon Milky Quartz <-- Not Miltank, either
Pokémon Smoky Quartz <-- Or Torkoal
Pokémon Tiger's Eye <-- Or Raikou, for that matter
Pokémon Citrine
Pokémon Prasiolite
Pokémon Rutilated Quartz
Pokémon Dumortierite Quartz

The third version is also split into 18 versions, with each variety of quartz having metallic vapour added to turn them into rainbow quartz ('aqua aura' won't sell as much as 'rainbow quartz'). Thus, 18 more versions of pretty much the same game:

Pokémon Rainbow Herkimer Diamond
Pokémon Rainbow Rock Crystal
Pokémon Rainbow Amethyst
Pokémon Rainbow Ametrine
Pokémon Rainbow Rose Quartz
Pokémon Rainbow Chalcedony
Pokémon Rainbow Carnelian
Pokémon Rainbow Aventurine
Pokémon Rainbow Agate
Pokémon Rainbow Onyx
Pokémon Rainbow Jasper
Pokémon Rainbow Milky Quartz
Pokémon Rainbow Smoky Quartz
Pokémon Rainbow Tiger's Eye
Pokémon Rainbow Citrine
Pokémon Rainbow Prasiolite
Pokémon Rainbow Rutilated Quartz
Pokémon Rainbow Dumortierite Quartz

r/Pokémon will buy all 36 versions of the same game, like they bought 4 versions of SM. If they're on Switch and a Switch game costs $60, 60x36 = $2160 willingly paid by r/pokemon members. I'm only half kidding.

* = not really