I spend a lot of time in Jasper National Park, in Alberta. It's quite a bit less commercial than Banff, and you can get away from the throngs of tourists quite easily by stepping into the backcountry.
Though I've never been, I've heard nothing but good things about Waterton Lakes National Park in Alberta, which is contiguous with Glacier National Park in Montana. I want very much to do a road trip through the southern parks, close to the US border. Grasslands National Park looks stunning from the photos I've seen, and Cypress Hills Interprovincial Park looks good too.
I've been to Gros Morne National Park, on the west coast of Newfoundland, and I cannot recommend that trip enough. It's got all the rugged mountain beauty of Banff and Jasper, combined with ocean, and there were hardly any tourists at all. The overnight ferry ride from Nova Scotia was really cool, too.
I live just a few miles from Riding Mountain National Park, which is 3000 km^2 of mixed boreal-aspen parkland in Manitoba. We've got a few sprawling vistas one can enjoy in solitude, and the wildlife viewing opportunities are definitely here. Moose, elk, black bears (highest density in North America), lynx, and wolves are relatively common, as are various owls and other birds that bird people like to watch in the early morning. I've got space to host if anyone wants to make the trip.