Well, I won't say which ones are my fave in Canada...but I'll give you my fave galleries in Toronto.
For institutional space, I think the Power Plant (Harbourfront Centre) is the most progressive and cutting edge space.
For large private galleries, it's easily Ydessa Hendeles on King W.
For small private galleries, I've really been impressed with Clint Roenisch Gallery on Queen West.
KGB