The Pokedex in the latest Pokemon X & Y is much more complex compared to all the previous generations Pokemon games. This is partly due to the Pokedex covering every species of Pokemon that has ever existed since the franchise debut.
If you plan to complete your Kalos Dex by bringing in Pokemon from previous versions to the latest Pokemon X & Y, you might want to do some re-thinking.
One gamer, who has achieved all the certificates and even the oval charm, revealed that his Kalos Dex still reads incomplete. After a thorough investigation, it was due to Buizel who came from older generation Pokemon games.
There is a remedy to this issue. In the above case, all the player has to do is capture a new Buizel in Pokemon X & Y and it should solve the problem. The Kalos Dex will register the Pokemon only if it is caught or hatch in the Kalos region.
Pokemon X & Y has been released for so long now. While the storyline might be done and dealt with by the players, most of them are struggling with the Kalos Dex. It appears to be getting harder with every Pokemon generation games.