I just bought Pokemon Alpha Sapphire for myself and Omega Ruby for my friend. I also played the X/Y games and I have Pokebank. The problem is: I didn't play games of the 5th and 4th generation. I basically skipped the Nintendo DS games and started playing again with the release of Pokemon X/Y.
My question is: Is it possible to complete the Pokedex with only the four 6th Gen games (X, Y, Omega Ruby, Alpha Sapphire)? Or will there be some unobtainable Pokemon?
I'm not talking about the rare legendary ones like Celebi, Arceus etc. I just want to know whether I need to use a 5th gen game or not to "Catch 'Em All".