You cannot get pokemon from Blue, red, yellow, gold, silver, and crystal, as they are not compatible with the GBA pokemon games.
The GBA games (ruby, sapphire, fire red, leaf green, emerald) are the oldest games you can get Pokemon from.
Using a Nintendo ds with a GBA port you can transfer Pokemon from GBA games to a gen 4 ds game. (diamond, pearl, plat, soul silver, heart gold)
From the gen 4 you need 2 Nintendo ds's, one will have the 4th gen game, while the 2nd would have a gen 5 game (black, white, B2, W2).
You can transfer the Pokemon from 4 to 5 using the wireless download play functions on the ds.
Now that the Pokemon are in the gen 5 games, you have to wait till December when the poke bank app releases which would allow you to transfer the Pokemon into the new Pokemon X and Y versions.
if anything isnt clear, feel free to pm me