With all due respect, I'm not Canadian and I find the OP's post somewhat insulting. He acts as if he's seen all of BC, YU and AB, although I wonder how long he spent touring those areas. Over a couple of years we've spent a couple of months in those areas and we know that we haven't come close to seeing it all. In AB alone, there is Jasper, Banff, the Columbia Icefields and, of course, the Calgary Stampede.
As for the rest of Canada there's a lot even before you get to Eastern Canada. Putting aside Niagara Falls because it's already been mentioned, there's Ottawa and all the Canadian national museums and more. There's Quebec City and all of Quebec Province; the closest you can have of being in Europe while still being in North America. This summer we "discovered" Tadoussac, north of Quebec City, which is one of the premier whale-watching locations in North America.
Once you get to the Maritime provinces there are many more things to see. To name just a few, there's Halifax, Peggy's Cove, Grand Pre, the fortress of Louisbourg, Charlottetown, several national parks in NB, PEI and NS, and lots more.
I strongly encourage you not to underestimate the richness of Canada, its culture and history. We spend most of our summers there and don't, by any means, think we've seen it all. This past summer we had the opportunity to spend two weeks in Newfoundland and wish we could have spent more time there.