Ever since the early years of Pokémon, this storied franchise has found success with a very specific formula. Each generation has had its original titles, offering variety with respective version exclusive Pokémon and various other differences per title. These releases have tested the water and established the new generation, before further additions are introduced. While the recent generations' games Sword & Shield and Scarlet & Violet have done this through DLC, the earlier generations introduced third titles instead.
Source：https://www.cbr.com/pokemon-all-third-version-games-ranked/
