My wife and I have lived in Fort Collins, Denver, and we currently live and invest in Colorado Springs. I second that each city has its own subculture, and even areas of the cities are unique. If you are moving to Denver I would ask what you value? Proximity to the mountains? Live on the west side. If you are looking for nice suburbs with good schools, look to the south Denver area. If you like city living, look into Washington Park, Platt Park, or the Highlands neigborhoods. A big reason that we, and many we know, left Denver was due to the housing prices.
Fort Collins is a great town to live in, has the small town feel with the big city benefits. Tons of parks, close to outdoor recreation (Horsetooth Reservoir), and a charming downtown strip with great restaurants, shops, and nightlife. All of Northern Colorado is blowing up with new developments and an influx of people.
Colorado Springs has been my favorite place to live so far. It has the best proximity to the mountains of anywhere I have lived in Colorado. You can see Pikes Peak from anywhere in town. The city is rapidly expanding north and east, and the downtown area has a long term development plan that is pretty exciting. There is a reason that is has been one of the top places to live year over year. It has its own unique subcultures as well, the Old Colorado City and Downtown areas attract many Millenials, and has a similar feel to Fort Collins Old Town area. North and east take you into sprawling suburbs. We chose to live and invest here in part because it is the most affordable prices compared to most areas on the front range (besides Pueblo), and it is a hub for tourism and transplants. I can't even go to the grocery store without meeting someone from Minnesota, so you would be in good company.
Hope this helps!