How come people can do this on the GTS and I can't?

Question

on the GTS people ask for cool Pokemon like Darkrai,Victini,Shaymin etc.
but when I offer a Pokemon I want a Pokemon like one of those but I can't.
Please help!

Answer 1

you need to be able to have that Pokemon in your pokedex sorce: experence
hope I helped

Answer 2

You need it in your pokedex first. They probably hacked a Pokemon, and they ask for good non hacked ones. Thats why I never use the gts.