Crystal shares Gold and Silver's 251 roster but changes where you find certain Pokemon. New encounter tables mean some species show up earlier or in different locations. Suicune is no longer a roaming legendary; it waits for you at Tin Tower as a guaranteed catch. The Move Tutor on Route 25 teaches Flamethrower, Thunderbolt, or Ice Beam once per week for free. Same Gen 2 Pokedex, slightly better access.
Hypno
Krabby
Kingler
Voltorb
Electrode
Exeggcute
Exeggutor
Cubone
Marowak
Hitmonlee
Hitmonchan
Lickitung
Koffing
Weezing
Rhyhorn
Rhydon
Chansey
Tangela
Kangaskhan
Horsea
Seadra
Goldeen
Seaking
Staryu
Starmie
Mr. Mime
Scyther
Jynx
Electabuzz
Magmar
Pinsir
Tauros
Magikarp
Gyarados
Lapras
Ditto
Eevee
Vaporeon
Jolteon
Flareon
Porygon
Omanyte
Omastar
Kabuto
Kabutops
Aerodactyl
Snorlax
Articuno
Still 251. Crystal didn't add new species. The roster carries over from Gold and Silver, but encounter tables are reshuffled, some Pokemon appear in new areas, and Suicune is a guaranteed catch instead of a roaming headache.
Suicune has a dedicated storyline and waits for you at Tin Tower instead of roaming randomly. New encounter tables add Pokemon to areas where they weren't before. The Move Tutor on Route 25 teaches Flamethrower, Thunderbolt, or Ice Beam for free once a week. And Crystal is the first Pokemon game that lets you pick a female player character.
Same starters as Gold and Silver: Cyndaquil, Totodile, and Chikorita. Cyndaquil is still the strongest start. Typhlosion's Speed and Sp. Atk carry through both regions. Totodile is solid if you want a physical Water type for the late game.
You encounter Suicune several times during the story, and Eusine (a new character) tracks it. After chasing it through Cianwood City and Route 42, it waits at the top of Tin Tower in Ecruteak City. Walk up and battle it. Level 40, one chance. Save before the fight.
Still Gen 2, Game Boy Color, 2000 in Japan. Crystal is Gold and Silver's definitive version. The 251 roster and two-region structure carry over, but Crystal adds a Suicune subplot, new encounter tables, and the first female player option.
Flamethrower, Thunderbolt, or Ice Beam. One move per week, taught by a man on Route 25. These are strong coverage moves that many Pokemon can't learn any other way in Gen 2. The cost is zero, just talk to him. Best move tutor deal in the series.
- Gen IY
Yellow151 Pokemon - Gen IRB

Red & Blue151 Pokemon - Gen IIGS

Gold & Silver251 Pokemon - Gen IIC
Crystal251 Pokemon - Gen IIIRS

Ruby & Sapphire386 Pokemon - Gen IIIFRLG

FireRed & LeafGreen386 Pokemon - Gen IIIE
Emerald386 Pokemon - Gen IVPt
Platinum493 Pokemon - Gen IVHGSS

HeartGold & SoulSilver493 Pokemon - Gen IVDP

Diamond & Pearl493 Pokemon - Gen VBW

Black & White649 Pokemon - Gen VB2W2

Black 2 & White 2649 Pokemon - Gen VIXY

X & Y721 Pokemon - Gen VIORAS

Omega Ruby & Alpha Sapphire721 Pokemon - Gen VIIUSUM

Ultra Sun & Ultra Moon807 Pokemon - Gen VIISM

Sun & Moon802 Pokemon - Gen VIILGPE

Let's Go Pikachu & Eevee153 Pokemon - Gen VIIISwSh

Sword & Shield664 Pokemon - Gen VIIIPLA
Legends: Arceus242 Pokemon - Gen VIIIBDSP

Brilliant Diamond & Shining Pearl493 Pokemon - Gen IXSV

Scarlet & Violet733 Pokemon - Gen IXLZA
Legends: Z-A364 Pokemon - Gen XWW

Winds & Waves51 Pokemon