I disagree.
It doesn't matter if your marriage is registered in Canada or not. Any legal marriage anywhere in this world is valid in Canada and hence needs to be listed in any sort of application. If you don't do that it could be considered "misrepresentation" (if they find out that you were married in Pakistan, which they probably will during their background checks) which could get you into serious trouble. You are never supposed to lie to CIC (and omitting information is equal to lying).