My daughter has had experience in both cities - she was a student at CSU for four and later worked for Boulder County as a parks and rec official for a few years. She was very happy with her four years in Fort Collins and talked about how much fun it was running and biking there. I don't recall what she said about variety. The Boulder experience was also good, but she said it was like living in yuppie hell - lots of trails, but lots of people. Constant friction between the runners vs. bikers - bikers vs. hikers - dog walkers vs. everyone else. Of course, her job entailed dealing with all these sub-groups. In the end, she felt that the Boulder area, while very chic, was just a little too whiney and political for her.
Just one daughter's opinion.