We often hear comparison between Chicago and Toronto. Here's a video about what makes Chicago's skyline interesting. What stood out to me was the row of heritage tower along the water and modern towers in the background, like Montreal (however, Montreal does the row of heritage downtown better IMO) and the towers along a park (feel like Ottawa and Vancouver are the only cities that have a prominent such feature). I'd say Winnipeg might offer the best variety of heights when looking at the skyline globally (not just Portage and Main) and Calgary in terms of variety.
• Video Link
I find Chicago has a more interesting skyline than Toronto when looking at it from a lower angle as it stretches along the lake, while Toronto's is deeper, so the point of interest is more from above. Seems to be due to the placement of the subway lines. Chicago has more variety while Toronto has more density.