Denver and Calgary do seem pretty similar to me, although Calgary definitely has the edge in terms of the number of highrises. They seem pretty analogous in some ways, but just looking at the satellite imagery (same scale) of the two cities shows a clear difference between US and Canadian planning/growth/governmental paradigms (the specifics of which I have no idea). The delineation between developed land and farmland is much more distinct in Canada (Calgary is more "bounded") and the growth seems to be more orderly to my eye. There are probably 2x as many people in the Denver shot, but they're probably contained in more than 2x the land area (less density). Another observation is that there are more distinct towns/cities in the Denver area whereas Calgary seems more centralized.
On a side note, I love downtown Denver and I've never been to Calgary so I can't say I can add much more to the conversation than this.