I haven't been to Flagstaff, so I can't speak about it directly, but I've heard some great stuff about it from people who have lived there. Supposedly it's very outdoors-y and has a good trail network. I think it's only around the 60,000 mark for population, though that's about equal to Loveland and is bigger than Grand Junction (~50,000), Fruita (~7000), and Crested Butte (~1500), all of which make your list. Flagstaff is also home to NAU. No downhill at the Snowbowl, though I've heard there are petitions to try to get them to build a bike park.
I've been spending increasing amounts of time in Flagstaff and plan to retire there. Mountain biking is excellent; Flag is surrounded by national forest lands that have lots of singletrack and forest roads. My family has a place there and the closest trails are 5 minutes away by bike. The current population is about 70,000 and it's a pretty well rounded town economically and sociologically for its size. Recent winters there have been widely variable, with little snow some years and huge amounts in others (53" in 4 days last week).
There are several large employers in town (Gore, Inc., NAU, NPS, USGS, Ralston Purina, to name a few) but the service jobs, in common with much of Arizona, don't pay very well. Housing is relatively expensive too.