I only know of two ubiquitous, essentially Canadian desserts (although there may be other more local specialties), and I'm not sure which one is the most popular in this country Dessert, or as we spell it "favorite".
The first was Nanaimo Bar, named after the British Columbia city but famous throughout the country. This is a no-bake square cake made of three layers: chocolate coconut lime crumb base, butter and custard center, and chocolate ganache on top, shaped into large slices and cut into individual sizes rectangular shape, like you would for brownies. Nanaimo bars are a staple dessert at elaborate events such as weddings and conferences. Sweeter and more decadent than a real brownie.
The second one is butter tart. Think of it like a mini pecan pie without the pecans. Except it can have pecans, raisins, walnuts, or chocolate. But its most classic version does not contain these things, just filling butter and sugar in a muffin base-sized shell. And there's no cornstarch or flour in the filling, so it's stickier than the non-walnut part of a pecan pie filling.
Butter tarts may be considered more rustic or less upscale than Nanaimo bars, and are best found at the gas station on a long road trip, on the counter of a roadside grocery store, and thanked the guy driving for the purchase of.
Like I said above, there are other more regional snacks, like blueberry grunt from the Maritimes or whatever, but they are probably too local to become a national favorite.
I'm not sure Quebec's sucre tartare is different enough from other countries' sugar pies to count as a unique dessert found nowhere else in the world. Beaver tails (basically pancake-shaped donuts with all kinds of funny stuff on them) are unique to Canada, but are really just a patented product from one company, so overall consumption isn't that high.
Anyway, I've never seen any statistics on the most popular desserts in Canada, but I wouldn't be surprised if something like cheesecake or ice cream is common in other countries as well . However, butter tarts and Nanaimo chocolate bars may also find a place on the list.