Well, Here is a List of all the Pokémon Catchable in both Fire Red and Leaf Green

No.	New Picture	US. Name
#001		Bulbasaur
#002		Ivysaur
#003		Venusaur
#004		Charmander
#005		Charmeleon
#006		Charizard
#007		Squirtle
#008		Wartortle
#009		Blastoise
#010		Caterpie
#011		Metapod
#012		Butterfree
#013		Weedle
#014		Kakuna
#015		Beedrill
#016		Pidgey
#017		Pidgeotto
#018		Pidgeot
#019		Rattata
#020		Raticate
#021		Spearow
#022		Fearow
#023		Ekans
#024		Arbok
#025		Pikachu
#026		Raichu
#027		Sandshrew
#028		Sandslash
#029		Nidoran
#030		Nidorina
#031		Nidoqueen
#032		Nidoran
#033		Nidorino
#034		Nidoking
#035		Clefairy
#036		Clefable
#037		Vulpix
#038		Ninetales
#039		Jigglypuff
#040		Wigglytuff
#041		Zubat
#042		Golbat
#043		Oddish
#044		Gloom
#045		Vileplume
#046		Paras
#047		Parasect
#048		Venonat
#049		Venomoth
#050		Diglett
#051		Dugtrio
#052		Meowth
#053		Persian
#054		Psyduck
#055		Golduck
#056		Mankey
#057		Primeape
#058		Growlithe
#059		Arcanine
#060		Poliwag
#061		Poliwhirl
#062		Poliwrath
#063		Abra
#064		Kadabra
#065		Alakazam
#066		Machop
#067		Machoke
#068		Machamp
#069		Bellsprout
#070		Weepinbell
#071		Victreebel
#072		Tentacool
#073		Tentacruel
#074		Geodude
#075		Graveler
#076		Golem
#077		Ponyta
#078		Rapidash
#079		Slowpoke
#080		Slowbro
#081		Magnemite
#082		Magneton
#083		Farfetch'd
#084		Doduo
#085		Dodrio
#086		Seel
#087		Dewgong
#088		Grimer
#089		Muk
#090		Shellder
#091		Cloyster
#092		Gastly
#093		Haunter
#094		Gengar
#095		Onix
#096		Drowzee
#097		Hypno
#098		Krabby
#099		Kingler
#100		Voltorb
#101		Electrode
#102		Exeggcute
#103		Exeggutor
#104		Cubone
#105		Marowak
#106		Hitmonlee
#107		Hitmonchan
#108		Lickitung
#109		Koffing
#110		Weezing
#111		Rhyhorn
#112		Rhydon
#113		Chansey
#114		Tangela
#115		Kangaskahn
#116		Horsea
#117		Seadra
#118		Goldeen
#119		Seaking
#120		Staryu
#121		Starmie
#122		Mr. Mime
#123		Scyther
#124		Jynx
#125		Electabuzz
#126		Magmar
#127		Pinsir
#128		Tauros
#129		Magikarp
#130		Gyarados
#131		Lapras
#132		Ditto
#133		Eevee
#134		Vaporeon
#135		Jolteon
#136		Flareon
#137		Porygon
#138		Omanyte
#139		Omastar
#140		Kabuto
#141		Kabutops
#142		Aerodactyl
#143		Snorlax
#144		Articuno
#145		Zapdos
#146		Moltres
#147		Dratini
#148		Dragonair
#149		Dragonite
#150		Mewtwo
#151		Mew
#161		Sentret
#162		Furret
#165		Ledyba
#166		Ledian
#167		Spinarak
#168		Ariados
#169		Crobat
#172		Pichu
#173		Cleffa
#174		Igglybuff
#175		Togepi
#176		Togetic
#177		Natu
#178		Xatu
#182		Bellossom
#183		Marill
#184		Azumarill
#186		Politoed
#187		Hoppip
#188		Skiploom
#189		Jumpluff
#193		Yanma
#194		Wooper
#195		Quagsire
#196		Espeon
#197		Umbreon
#198		Murkrow
#199		Slowking
#200		Misdreavus
#201		Unown
#202		Wobbuffet
#206		Dunsparce
#208		Steelix
#211		Qwilfish
#212		Scizor
#214		Heracross
#215		Sneasel
#218		Slugma
#219		Magcargo
#220		Swinub
#221		Piloswine
#223		Remoraid
#224		Octillery
#225		Delibird
#226		Mantine
#227		Skarmory
#230		Kingdra
#231		Phanpy
#232		Donphan
#233		Porygon2
#236		Tyrogue
#237		Hitmontop
#238		Smoochum
#239		Elekid
#240		Magby
#242		Blissey
#243		Raikou
#244		Entei
#245		Suicune
#246		Larvitar
#247		Pupitar
#248		Tyranitar
#249		Lugia
#250		Ho-oh
#298		Azurill
#360		Wynaut
#386		Deoxys