My favorite games of each Gen are R, S, S, LG, P, SS, B, W2, X, OR, S, US, and S.
No wait, nobody says that. Individual games are referred to by their full names. Paired games can be given an acronym using the first letters of each game along with the additional element.
Red and Green = RG
Gold and Silver = GS
Ruby and Sapphire = RS
Diamond and Pearl = DP
Black and White = BW
X and Y = XY
Sun and Moon = SM
Sword and Shield = SS
FireRed and LeafGreen = FRLG
HeartGold and SoulSilver = HGSS
Black 2 and White 2 = B2W2
Omega Ruby and Alpha Sapphire = ORAS
Ultra Sun and Ultra Moon = USUM
Let's Go Pikachu and Let's Go Eevee = LGPE
Blue = Blue, RGB when paired with RG
Crystal = Crystal, GSC when paired with GS
Emerald = Emerald, RSE when paired with RS
Platinum = Platinum, DPPt when paired with DP
Pt is used to distinguish Platinum from Pearl because the games are grouped together and literally right next to each other in listings. Pt is also used in South Korea.
Sword and Shield have no risk of being confused with SoulSilver because they're unrelated to each other, and SoulSilver is only SS when immediately preceded by HG.