There is lots to see and do in the Niagara area I'd go back if time permits. I haven't thought about a bucket list but a few quick ideas would be:
A couple months in the Queen Charlotte's Islands. If you can find "Ravens and Eagles" on your TV or an aboriginal station it is very spiritual.
Northern Lights (anywhere).
A cruise with naturetrek.ca or a shorter trip on the MV Lady Rose out of Port Alberni on the west coast of Vancouver Island.
Hike the west coast trail (Vancouver Island again) or Cape Scott (northern tip of Vanc Isl) and/or Botanical Beach near Port Renfrew at the start of the southern end of the west coast trail.
On the East Coast I'd definitely like to see New Brunswick, the Bay of Fundy, Northumbrian Strait, PEI, Nova Scotia (especially the Citadel) and Cape Breton.
Palenque and Chitzen Itza.
Terry Fox statue, near Thunder Bay (marking the end of his run)
The beaches of Normandy, France (on a June 6th) (it's a guy thing).
Stonehenge
Prague
Sedona, Arizona
Santa Fe, New Mexico
I'm going to give it some more thought and no doubt my wife will change my priorities somewhat (for the better) but we will soon fulfill a wish to travel to SEAsia.
Have fun with the list.