For an overall view, 19th between Yonge and Bayview is unbeatable. Scarborough to Mississauga, and everything in between. Drop Zone lift 4 is a very close second.
For downtown and midtown, my favourite view is from the TTC parking lot at Fairview. I would assume that the 34th floor apartments at Yonge and Steeles have an even better view, but I've never been up there.
For NYCC, its German Mills park, just north of Steeles on Don Mills.
For Don Mills/Leaside, its Thornlea Park. Bayview south of 7.
When you're at the top of the CN tower, looking north you see a little hill on the horizon. This hill is at about 19th-Stouffville road. Driving south down this hill on either Bayview or Yonge offers a great view.