How many pokemon are legitimately obtainable in Pokemon X and Y? I'm talking about only these 6th gen games and by legitimately I mean by catching, breeding and trading only between those two games (no pokebank, hacking or events).
125 from older games are not obtainable in X/Y. Also you can't get Diancie. So you can get 593 Pokémon from the 719 in all.
You can take a look here which Pokémon are only available at a speciffic version: Pokemon X
Pokémon which are not available in X/Y (in German): not in Pokémon X/Y