Speaking to EB Games myself I was informed that SE is distributing the preorder codes to them at regular intervals, and from there EB Games will send them to customers according to chronological order of their preorder, so those who preordered recently hence have to wait a little bit (like myself) - the ones who have received their codes already will be those who preodered early on.

I know it's annoying, a friend of mine was sent their code last week and has already registered it and is ready to go, where as I'm like you and still waiting for my preorder code (my friend got the standard edition though, where as my order is for the Collector's Edition).

Either way, EB told me to wait another week or two and if I still haven't received it, to get back in touch with them and to see what they can do (apparently they're meant to be receiving more codes from SE within the next week or so).