The problem with Canada is that most provinces have provincially run liquor monopolies. They're usually better than an American gas station for selection, but not as good as any beer store worth its salt. The LCBO (Ontario) has a killer wine list, though, and it looks like they're expanding their beer selection.
Quebec is good for beer. Unibroue in the corner stores. If you visit Montreal, visit the brewpubs, especially Dieu du Ciel! - (amazing amazing amazing place!), Le Cheval Blanc, L'amère a Boire for good lagers, Benelux for Benelux beers. Have a meal at Fourquette Fourchette, the Unibroue mecca in-town. They cook with it and everything.
In some provinces, there are a few licensed private stores, but you kinda have to live there to know where to find them.
Cheers,
Kai