I can pretty much guarantee you that most people who voted for Douglas did so for one reason: He is considered the forefather of Medicare. I'd be very surprised if they were familar with anything else he stood for politically.
Of course, it would also be terribly unfair to totally dismiss Douglas just because he was a socialist. He did great things for the province of Saskatchewan when he was leader. At the time, he was heartily embraced by the people there and is remembered fondly (Being from Saskatchewan I've discussed this with the old timers there).
He was elected to five terms in Sask., so you can mock him if you will, but the people at the time seemed to think he was doing something right.
But is he the greatest ever Canadian? Well, not in my book.
That honour would go to James Randi!!