Yep. Canadians would want to include that sport, and his name would be there way above any else's. I know nothing about ice hockey (sorry, mate, that's what we call it in countries where it isn't played at any serious level), but as soon as I saw footage of Gretzky, his greatness jumped out of the screen at you.
Ali's status goes way, way beyond that of a mere athlete. I travelled widely in Africa in 1975-6, and the entire continent was simply in love with him. His stand on the Vietnam war made him a hero to many people who didn't give a damn about boxing. Billy Crystal's funeral eulogy (the best I've ever heard) says everything that needs to be said.
Football: for me, it is, hands down, Pelé. Three times a World Cup winner? Sorry, did you say three? Oh, and the small matter of over a thousand goals, at a time when the Brazilian league was still a serious proposition, because all their players hadn't been poached by Europe.