The following Pokemon are completely unobtainable in XY without trading from ORAS or transferring from a different generation. Evolutionary lines are ordered by their first appearing member in National Pokedex order.
Rattata
Meowth
Koffing
Porygon
Mew
Chikorita
Cyndaquil
Totodile
Misdreavus
Unown
Stantler
Raikou
Entei
Suicune
Lugia
Ho-oh
Celebi
Treecko
Torchic
Mudkip
Slakoth
Baltoy
Feebas
Regirock
Regice
Registeel
Latias
Latios
Kyogre
Groudon
Rayquaza
Jirachi
Deoxys
Turtwig
Chimchar
Piplup
Kricketot
Cherubi
Buneary
Glameow
Finneon
Uxie
Mesprit
Azelf
Dialga
Palkia
Heatran
Regigigas
Giratina
Cresselia
Phione
Manaphy
Darkrai
Shaymin
Arceus
Victini
Snivy
Tepig
Oshawott
Cottonee
Darumaka
Yamask
Frillish
Tynamo
Elgyem
Bouffalant
Cobalion
Terrakion
Virizion
Tornadus
Thundurus
Reshiram
Zekrom
Landorus
Kyurem
Keldeo
Meloetta
Genesect
The following families can be found through Friend Safari, but are listed here because encountering them is an inconsistent endeavour.
Clefairy
Vulpix
Paras
Venonat
Mankey
Growlithe
Ponyta
Seel
Grimer
Drowzee
Krabby
Hitmonlee
Chansey
Tangela
Electabuzz
Magmar
Togepi
Natu
Aipom
Sunkern
Girafarig
Pineco
Phanpy
Wurmple
Seedot
Shroomish
Numel
Cacnea
Duskull
Tropius
Snorunt
Spheal
Beldum
Shinx
Shellos
Bronzor
Spiritomb
Lillipup
Munna
Pidove
Blitzle
Drilbur
Tympole
Sewaddle
Petilil
Maractus
Minccino
Deerling
Joltik
Klink
Rufflet
Vullaby
Larvesta
List of Pokemon by availability (Bulbapedia)
