I believe most Canadians are Irish :)
All depends how you calculate it.
For example, how many generations back are we talking? For me, my grandparents were born in Canada, and most of their parents were too. But before that, most weren't. A lot came from Ireland.
So for me, I calculate it by going back 6 generations. We all have 64 great-great-great-great-grandparents. It took me all year, but I've traced down most of them. It turns out, about 20 of them were from Ireland. So I'm almost 1/3 Irish, measured that way.
But unless you're dark-skinned, if you're Canadian, you're probably Irish :D