Yes, we have similar questions for Manhattan and London, but having just moved to Vancouver I'm keen to find something here - there are a lot of skyscrapers downtown, but I know nothing about them.
Either downtown with a good view of the harbour and mountains, or maybe elsewhere with a good view of downtown. It doesn't need to be a building, just be easy to get to, cheap or free, and publicly available.
So Grouse Mountain probably doesn't work, as it is currently covered in snow and costs to get up, and is far away, although I've been told the views are spectacular.