Pairs are consistently said in a specific order, with one game always getting front billing.
Red and Green (not Green and Red)
Gold and Silver (not Silver and Gold)
Ruby and Sapphire (not Sapphire and Ruby)
FireRed and LeafGreen (not LeafGreen and FireRed)
Diamond and Pearl (not Pearl and Diamond)
HeartGold and SoulSilver (not SoulSilver and HeartGold)
Black and White (not White and Black)
Black 2 and White 2 (not White 2 and Black 2)
X and Y (not Y and X)
Omega Ruby and Alpha Sapphire (not Alpha Sapphire and Omega Ruby)
Sun and Moon (not Moon and Sun)
Ultra Sun and Ultra Moon (not Ultra Moon and Ultra Sun)
Let's Go Pikachu and Let's Go Eevee (not Let's Go Eevee and Let's Go Pikachu)
Sword and Shield (not Shield and Sword)
Brilliant Diamond and Shining Pearl (not Shining Pearl and Brilliant Diamond)
Scarlet and Violet (not Violet and Scarlet)
Charizard, Ho-Oh, Groudon, Dialga, Reshiram, Xerneas, Solgaleo, Zacian, Koraidon
Venusaur, Lugia, Kyogre, Palkia, Zekrom, Yveltal, Lunala, Zamazenta, Miraidon
And if I remember correctly, SoulSilver outsold HeartGold.
