u/Usersief

Here is the list ordered from lowest to highest sales:

Let's Go, Pikachu! & Let's Go, Eevee! (2018) - 15.07 million copies

Pokémon Black and White (2010) - 15.64 million copies

Pokémon Ruby and Sapphire (2002) - 16.22 million copies

Pokémon Sun and Moon (2016) - 16.34 million copies

Pokémon X and Y (2013) - 16.80 million copies

Pokémon Diamond and Pearl (2006) - 17.67 million copies

Pokémon Gold and Silver (1999) - 23.10 million copies

Pokémon Sword and Shield (2019) - 27.16 million copies

Pokémon Scarlet and Violet (2022) - 28.28 million copies

Pokémon Red, Green, and Blue (1996) - 31.38 million copies

List of all regional birds from Generation 1 to 9:

Generation 1 (Kanto): Pidgey, Pidgeotto, Pidgeot

Generation 2 (Johto): Hoothoot, Noctowl

Generation 3 (Hoenn): Taillow, Swellow

Generation 4 (Sinnoh): Starly, Staravia, Staraptor

Generation 5 (Unova): Pidove, Tranquill, Unfezant

Generation 6 (Kalos): Fletchling, Fletchinder, Talonflame

Generation 7 (Alola): Pikipek, Trumbeak, Toucannon

Generation 8 (Galar): Rookidee, Corvisquire, Corviknight

The Nine Pokémon Generations:

Generation I (1996): Red, Blue, Green, Yellow (Region: Kanto)

Generation II (1999): Gold, Silver, Crystal (Region: Johto)

Generation III (2002): Ruby, Sapphire, Emerald, FireRed, LeafGreen (Region: Hoenn)

Generation IV (2006): Diamond, Pearl, Platinum, HeartGold, SoulSilver (Region: Sinnoh)

Generation V (2010): Black, White, Black 2, White 2 (Region: Unova)

Generation VI (2013): X, Y, Omega Ruby, Alpha Sapphire (Region: Kalos)

Generation VII (2016): Sun, Moon, Ultra Sun, Ultra Moon, Let's Go, Pikachu!, Let's Go, Eevee! (Region: Alola)

Generation VIII (2019): Sword, Shield, Brilliant Diamond, Shining Pearl, Legends: Arceus (Region: Galar/Hisui)

Generation IX (2022): Scarlet, Violet, Legends: Z-A (Region: Paldea)