I guess its all about giving a good impression and having better chances if you have GRE with a good score and its only going to matter for universities which are at the top-notch, considering UBC, McGill, ualberta etc. As for other universities it doesnt matter at all.
I have got acceptance at Dalhousie without the GRE. But I'm not going there and would take my chances on UBC & McGill. But for that, I am definitely going to take GRE first.
P.S GRE is applicable for graduate studies only