Heartgold and Soulsilver, Black and White, and so many other titles out there. Can you come up with one?
Example:
Pokemon Amber

Pokemon Lead and Pokemon Chrome.

Pokemon Silicon and Velvet

Pokemon Galaxy and Nebula

Pokemon Uranium
Pokemon Iridium
Pokemon Titanium
Pokemon Crimson

Pokemon Frost and Pokemon Drought
C'mon people, stop naming Minerals

Pokemon Teal and Pokemon Crimson.
What's wrong with naming minerals?

Humm....Pokémon Terra and Pokémon Celestia

Coming Soon
Pokemon: Time Edition and Pokemon: Money Edition

Embark on an all new rehash adventure through the Busisus Region! You'll embark a quest to collect the eight Gym Diplomas and defeat the mysterious Team Conspiracy!

Stay tuned because in a year, Pokemon: Marketing Strategy Edition will be announced, featuring alternate formes and a slightly cooler storyline!

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Pokémon Metal and Pokémon Iron

I am not that creative, but maybe Pokémon Pop and Pokémon Rock. Music for a change?

Pokemon Dark. Dark types get all stats boosted by 10.

And Pokemon Light. Only berries in this game. Candy isn't healthy.

I was thinking Pokémon Cobalt and Crimson. Both are metals. Cobalt is blue, while Crimson is red. I was also thinking that the soundtrack could have classic rock influences. Maybe something 70's or 50's, perhaps.

Pokemon Purple, Orange, Brown, Gray <3

pokémon plasma and nuclear versions

Pokemon Derp and Nerp versions

Pokemon Gray
Pokemon Nova
Pokemon: The Return of Rocket

What about Pokemon Amathyst with Arceus on the cover

Pokemon Violet Version

Pokemon Purple. Spotlight for Mewtwo? and Pokemon clearPink- for Mew

Something relating to the legendaries. Like D/P for instance...
Pokémon Endless Time and Limitless Space Versions
or to be general
Pokémon Blazing Fury Version

I'm thinking about the possibility of there being a Pokemon Chrome and Pokemon Bronze.

[Pokemon]: Digimon Evolution
....
Or Pokemon: the Battle against Marxism...
trolololololol

My favorite color, Pokémon Turquoise.
Maybe something seasonal based, too. Pokémon Bright Summer and Pokémon Chilling Winter.

Pokemon Crude Oil and Natural Gas. I'm taking the commodities route.

Pokemon Charged Yellow (Remake of Yellow)

Hmm...no good R/S/E names?

RevampedRuby?
SuperchargedSapphire?

Pokémon Radiating Ruby and Storming Sapphire Versions.

Pokemon Mythical, Mystical, and Mysterious!