>>31856046Serebii has a list of Pokémon Unobtainable for each game (doesn't includes Version Exclusives). If you want to know which Pokémon can only be found on XY then see the ORAS Unobtainables and compare it with SM, if you want to know which ones can only be found on ORAS then see the XY Unobtainables and compare it with SM.
For example: Ekans, Nidoran, Bellsprout, Yanma, Houndour, Burmy, Stunky, Golett, Pawniard, Scatterbug, and Noibat lines are some of the ones that can only be caught in XY.
