Route 10: 44 species in 8 games

Road 10: 44 species across 14 versions

Red and Green (Japan): 8 species
Species	Method	Levels	Chance	Game page
Spearow	Walking in tall grass or a cave	13 to 17	35%	All places
Ekans	Walking in tall grass or a cave	11 to 17	25%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Poliwhirl	Fishing with a super rod	23	50%	All places
Slowpoke	Fishing with a super rod	15	50%	All places
Voltorb	Walking in tall grass or a cave	14 to 17	40%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Red and Blue: 8 species
Species	Method	Levels	Chance	Game page
Spearow	Walking in tall grass or a cave	13 to 17	35%	All places
Ekans	Walking in tall grass or a cave	11 to 17	25%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Poliwhirl	Fishing with a super rod	23	50%	All places
Slowpoke	Fishing with a super rod	15	50%	All places
Voltorb	Walking in tall grass or a cave	14 to 17	40%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Yellow: 12 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	18	20%	All places
Raticate	Walking in tall grass or a cave	20	5%	All places
Nidoran♀	Walking in tall grass or a cave	17	10%	All places
Nidoran♂	Walking in tall grass or a cave	17	10%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Machop	Walking in tall grass or a cave	16 to 18	5%	All places
Magnemite	Walking in tall grass or a cave	16 to 22	50%	All places
Krabby	Fishing with a super rod	15 to 20	70%	All places
Kingler	Fishing with a super rod	25	10%	All places
Horsea	Fishing with a super rod	10	20%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Gold and Silver: 9 species
Species	Method	Levels	Chance	Game page
Raticate	Walking in tall grass or a cave	16 to 18	up to 25%	All places
Spearow	Walking in tall grass or a cave	16	up to 30%	All places
Fearow	Walking in tall grass or a cave	18	up to 10%	All places
Voltorb	Walking in tall grass or a cave	17	up to 30%	All places
Goldeen	Fishing with a good rod	20	65%	All places
Goldeen	Fishing with an old rod	10	15%	All places
Goldeen	Fishing with a super rod	40	70%	All places
Goldeen	Surfing	10 to 19	90%	All places
Seaking	Fishing with a super rod	40	10%	All places
Seaking	Surfing	15 to 19	10%	All places
Electabuzz	Walking in tall grass or a cave	15 to 17	up to 10%	All places
Magikarp	Fishing with a good rod	20	35%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places
Quagsire	Walking in tall grass or a cave	16 to 17	up to 40%	All places

Crystal: 12 species
Species	Method	Levels	Chance	Game page
Raticate	Walking in tall grass or a cave	15	up to 20%	All places
Spearow	Walking in tall grass or a cave	15	up to 30%	All places
Fearow	Walking in tall grass or a cave	15	up to 10%	All places
Zubat	Walking in tall grass or a cave	15	5%	All places
Venonat	Walking in tall grass or a cave	15	30%	All places
Venomoth	Walking in tall grass or a cave	15	10%	All places
Voltorb	Walking in tall grass or a cave	17	up to 30%	All places
Marowak	Walking in tall grass or a cave	15	up to 5%	All places
Goldeen	Fishing with a good rod	20	65%	All places
Goldeen	Fishing with an old rod	10	15%	All places
Goldeen	Fishing with a super rod	40	70%	All places
Goldeen	Surfing	10 to 19	90%	All places
Seaking	Fishing with a super rod	40	10%	All places
Seaking	Surfing	15 to 19	10%	All places
Electabuzz	Walking in tall grass or a cave	16	up to 5%	All places
Magikarp	Fishing with a good rod	20	35%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places

FireRed: 9 species
Species	Method	Levels	Chance	Game page
Spearow	Walking in tall grass or a cave	13 to 17	35%	All places
Ekans	Walking in tall grass or a cave	11 to 17	25%	All places
Psyduck	Fishing with a super rod	25 to 35	1%	All places
Tentacool	Surfing	5 to 40	100%	All places
Krabby	Fishing with a good rod	5 to 15	20%	All places
Voltorb	Walking in tall grass or a cave	14 to 17	40%	All places
Horsea	Fishing with a good rod	5 to 15	60%	All places
Horsea	Fishing with a super rod	15 to 35	84%	All places
Magikarp	Fishing with a good rod	5 to 15	20%	All places
Magikarp	Fishing with an old rod	5	100%	All places
Gyarados	Fishing with a super rod	15 to 25	15%	All places

LeafGreen: 9 species
Species	Method	Levels	Chance	Game page
Spearow	Walking in tall grass or a cave	13 to 17	35%	All places
Sandshrew	Walking in tall grass or a cave	11 to 17	25%	All places
Tentacool	Surfing	5 to 40	100%	All places
Slowpoke	Fishing with a super rod	25 to 35	1%	All places
Krabby	Fishing with a good rod	5 to 15	60%	All places
Krabby	Fishing with a super rod	15 to 35	84%	All places
Voltorb	Walking in tall grass or a cave	14 to 17	40%	All places
Horsea	Fishing with a good rod	5 to 15	20%	All places
Magikarp	Fishing with a good rod	5 to 15	20%	All places
Magikarp	Fishing with an old rod	5	100%	All places
Gyarados	Fishing with a super rod	15 to 25	15%	All places

HeartGold and SoulSilver: 14 species
Species	Method	Levels	Chance	Game page
Raticate	Walking in tall grass or a cave	16 to 18	up to 20%	All places
Spearow	Walking in tall grass or a cave	16	up to 20%	All places
Fearow	Walking in tall grass or a cave	18	up to 10%	All places
Voltorb	Walking in tall grass or a cave	17	up to 20%	All places
Goldeen	Fishing with a good rod	20	60%	All places
Goldeen	Fishing with an old rod	10	15%	All places
Goldeen	Fishing with a super rod	40	70%	All places
Goldeen	Surfing	10 to 15	90%	All places
Seaking	Fishing with a super rod	40	10%	All places
Seaking	Surfing	15	10%	All places
Electabuzz	Walking in tall grass or a cave	15 to 18	up to 5%	All places
Magikarp	Fishing with a good rod	20	40%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places
Zapdos	Static encounter	50	100%	All places
Quagsire	Walking in tall grass or a cave	16 to 18	up to 30%	All places
Linoone	Walking in tall grass or a cave	16	20%	All places
Whismur	Walking in tall grass or a cave	16 to 17	20%	All places
Bidoof	Walking in tall grass or a cave	16	20%	All places
Buizel	Walking in tall grass or a cave	16 to 17	20%	All places

Let's Go, Pikachu and Eevee: 20 species
Species	Method	Levels	Chance	Game page
Charizard	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Rattata	Walking in the overworld	18 to 23	100%	All places
Raticate	Walking in the overworld	18 to 23	100%	All places
Spearow	Walking in the overworld	18 to 23	100%	All places
Spearow	Flying pokemon in the sky	3 to 56	100%	All places
Fearow	Walking in the overworld	18 to 23	100%	All places
Fearow	Flying pokemon in the sky	3 to 56	100%	All places
Nidoran♀	Walking in the overworld	18 to 23	100%	All places
Nidorina	Walking in the overworld	18 to 23	100%	All places
Nidoran♂	Walking in the overworld	18 to 23	100%	All places
Nidorino	Walking in the overworld	18 to 23	100%	All places
Tentacool	Surfing in the overworld	18 to 23	100%	All places
Tentacruel	Surfing in the overworld	18 to 23	100%	All places
Krabby	Walking in the overworld	18 to 23	100%	All places
Chansey	Rare spawn in grass with lure or catch combo	18 to 23	100%	All places
Magikarp	Surfing in the overworld	18 to 23	100%	All places
Articuno	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Zapdos	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Moltres	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Dratini	Surfing in the overworld	18 to 23	100%	All places
Dragonair	Surfing in the overworld	18 to 23	100%	All places
Dragonite	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places