You can catch ~450 of the pokemon IN GAME, but the rest you need to transfer from previous GBA files in the Pal Park. The only ones you can't catch are previous starter and jedgendary pokemon. So you can't catch Bulbasour Rayquaza, Cyniquil etc.
One person's experience or opinion never shows the general consensus
PSN ID: Tispower
MSN: tispower1@hotmail.co.uk