We just visited River Run at Granby last week. Brand new; lots of noisy construction still going on; absolutely no shade (and I know Granby gets warm because I spent 3 months there on a job); some paved, some gravel, pull-thru and back-in sites; rental Airstreams; a tiny home village; and right at the noisy intersection of US 40 and US 34. With the prices they are charging ($90+/night), I wouldn't stay there if they gave me a 50% discount. I would much rather stay at the USFS Stillwater campground on Lake Granby because River Run is still a significant drive to Lake Granby, Grand Lake, or Rocky Mountain NP!
Now that rant is out of the way, I'll add a few positive comments. Having lived in Colorado 57 years and my wife and I having worked all over the state, we have a few favorite areas that we keep going back to with the fifth wheel. One of them is Ridgway State Park, as mentioned by others. But, yes, it does have a 14-day limit. However, we mainly stay there in the fall color season to photograph Mt. Sneffles and Telluride. In that general area of the San Juans, we also enjoy Ouray, Dolores, and Durango, where one of our sons went to college.
We have stayed in a Glenwood Springs RV park for a club event, but would not stay there long term--too much train, as well as I-70, noise. We prefer to go south to the Gunnison-Crested Butte area--higher, usually cooler, and better fishing. The Gunnison River, Taylor River, and Blue Mesa Reservoir have some of the best trout fishing in Colorado. From there, you can easily visit Black Canyon of the Gunnison NP and Lake City; take a boat trip through the Black Canyon on Morrow Point Reservoir; go whitewater rafting; rent an OHV and drive it over Cumberland, Pearl, or Schofield Pass; take a picnic lunch to ghost towns like Ruby, Irwin, Tincup, or Powderhorn; "track" abandoned narrow-gauge railroads to the Alpine Tunnel, over Marshall Pass, or up Ohio Creek; and visit the CPW's Roaring Judy Fish Hatchery. However, not being a golfer, I have no idea how the golf courses are there.
We love the scenery in the Lake City area in fall, too, but not long term. It is no longer a Colorado town. Hinsdale County is "Little Texas" where nearly every shop, cafe, motel, RV park, and OHV-snowmobile rental/sales dealer is owned and operated by Texans. That may not be a disadvantage to you, but I know of no golf courses there either.
You might want to add the Steamboat Springs area to your "research list" too. It has enough elevation to stay cool, enough population to support medical facilities, and a ski area to provide upscale amenities (restaurants, golf, hot springs pools and spas, gondola and hot air balloon rides, summer festivals, etc.). It also has whitewater rafting; hiking to scenic waterfalls; boat, canoe, and kayak rentals; and good fishing at Steamboat, Stagecoach, and Pearl Lake and Yampa River state parks.
"Retirement is the best job I ever had!"
2015 RAM 2500 4x4 crewcab 6.7L CTD; 2016 Rockwood Signature UltraLite 5th wheel