I've been going to Canada's Wonderland since grade 10, and I have owned the season pass for 4 years.
There are a lot of different rides to choose from, something that my mom can go on, to something a thrill seeker like me would enjoy. The rides are relatively close to each other so you really don't need to walk very far to get to one another. They also have shows going on which are included in your admission, so you can watch them for free.
Canada's Wonderland is owned by an American company - Cedar Fair. Amusement parks in the US don't have 1-3 hour lines like we do. They also usually have estimated wait times (which are extremely accurate), which we don't have. It's a great place to go if you have extra time and love rollercoasters while on vacation, of if you're around here and you have the time to just go line up. Otherwise, it's really not that special.
The waterpark is decent, but my biggest tip is to go early and leave early. It starts to get really stinky after 1pm when visitors increase.