In order of most expensive to least: Vancouver, Victoria, Toronto, Montreal.
Vancouver -- lower mainland population 2.5 millions (offers a good blend of city & outdoor attractions/activities) with the most divert ethnic restaurants in Canada, maybe the most divert in North America.
Victoria -- a sleepy town with lots of outdoor attractions/activities (UVic is the prettiest campus in Canada, and is a good study environment, low activity/distractions), that offers most things that you can find in a large city, and more just a ferry ride away.
Toronto -- is the largest city in Canada.
Montreal -- is the place to be for parties in Canada.