Legendary Pokémon that have been confirmed
With Pokémon X, Pokémon Y, Pokémon Omega Ruby, and Pokémon Alpha Sapphire, every Legendary Pokémon discovered to date can be obtained!
Of course there will be the Legendary Pokémon that are part of the main story and that also appeared in the original Ruby and Sapphire.
These include:
- Groudon (Omega Ruby)
- Kyogre (Alpha Sapphire)
- Rayquaza
- Latios (Omega Ruby)
- Latias (Alpha Sapphire)
- Deoxys
The Regi trio also makes a return, this time along with Regigas.
These obviously include:
- Regirock
- Regice
- Registeel
- Regigas
Now that Mirage Spots have been revealed, more Legendary Pokémon have been confirmed to make an appearance.
These include:
- Raikou
- Entei
- Suicune
- Uxie
- Mesprit
- Azelf
- Coballion
- Terrakion
- Virizion
- Tornadus
- Thundurus
- Landorus
- Cresselia
- Heatran
However, in regard to the Mirage Spots, it is important to note:
Legendary Pokémon you'll encounter sometimes vary based on which game you're playing.
Some Pokémon appear somewhere in the game, though we are not yet sure.
These definitely include:
- Ho-Oh
- Lugia
- Palkia
- Dialga
- Zekrom
- Reshiram
Here is a link to the official video
And here is a list of Pokémon confirmed to be in OR/AS
So that leaves us with the Legendary Pokémon that haven't been confirmed
Based on the original statement, (assuming it is correct);
>With Pokémon X, Pokémon Y, Pokémon Omega Ruby, and Pokémon Alpha Sapphire, every Legendary Pokémon discovered to date can be obtained!
That also (presumably) means that these Pokémon can also be found in OR or AS, although they are not confirmed:
- Mew
- Jirachi
- Giratina
- Darkrai
- Shaymin
- Manaphy
- Victini
- Arceus
- Kyurem
- Keldeo
- Meloetta
- Genesect
That leaves us with very few that will almost assuredly not appear in either game:
- Xerneas
- Yvetal
- Zygarde
- Diancie
- Mewtwo
- Zapdos
- Moltres
- Articuno