Maybe I'm still burnt out by seeing so many churches and cathedrals on my tour of Germany in September 2015, but I didn't see anything terribly spectacular about Nortre-Dame over other cathedrals of this stature. It's beautiful, but if you've been oin one cathedral, you've kind of been in them all as far as I'm concerned, and a $15 CAD price tag isn't going to make me feel better about visiting.
If you're really into churches, Nortre-Dame should certianly be on your list to visit, but don't go out of your way.