What credit cards does the real Canadian superstore accept?

Literally tens of thousands of retailers across Canada accept American Express for payment. The better question is who doesn't. The best way to find out if a particular store does is to call them or visit their website.

Very few retailers accept American Express exclusively. Most will honor Visa and MasterCard for purchases as well. The exception is stores and venues that have an advertising agreement with a particular card service, such as Vancouver's 2010 Olympic games, which were co-sponsored by Visa, and Costco, which issues its own American Express card, and does not accept other cards (other than debit).