As for 'NYC-style Canyons', only a few come to mind, namely certain stretches of streets that run in the financial district, but even they don't contend the claustrophobic, tight and tall canyons lining avenues in Midtown Manhattan. As for Yonge Street, I've never found anything particularly interesting from a density or height perspective, so for me, I have a hard time comparing it to an NYC one. However, what's exciting what it will become in a short period of time. Particularly in the stretch from Queen north to Bloor. There are going to be dozens of condos sprouting up on either side of the street, blending in with many of the pre-existing older aesthetics that currently run along Yonge. It's really going to be something of its own to witness. People won't even recognize Yonge in a decades time. Think of it as the transformation happening in the Entertainment district, but along a single street, main street.
You're right steveve, we don't have anything that truly compares to awesome midtown canyons in Manhattan. But we do have some contenders. I think Yonge St. is one of them, as we speak, because, when looking at it from the foot of Front, it stretches longer than any of our other canyons (minus perhaps Bay St., though let's note that its canyon really only starts N of Queen), and there is a large number of high-rises going up the street.
Regardless, I'd be willing to get into a physical altercation about true canyons in Toronto if pushed hard enough.