Colorado Backpacking Trip

Look at the Uncompaghre Wilderness Near Ouray. RMNP is gorgeous but lots of hoops for backpacking.

That does look nice. However, it is over 5 hours from the airport.

No ideas for you, but just a note that if you do camp in RMNP you will need a bear can and a reservation. IPW also requires reservation.

The Sangre De Cristo mountains would be a bit less of a drive (save a couple hours). They have many opportunities for out and backs, as well as a few loop options.

Edit: Comparing the drive to the San Juan's, which were recommended.

What is your acceptable range of travel in the car? A few options have already been pointed out. Where do you do you ski trips? Might be nice to see some of the same terrain in the summer or a new place entirely. You brought up RMNP which a lot of people pick for the scenery and the proximity to the Denver airport. However, a lot of people pick RMNP. Some people like the crowds while others don't. Sangre's would be a fairly quiet affair unless it's a holiday weekend and would allow you the opportunity of some 14ers.

EDIT: What time of year are you expecting to come? Might play a role in our recommendations to you.

If needed, we could travel up to 5 hours. However, if there is something just as satisfying that is closer, then I’d prefer that.
Our ski trips are at Vail resorts (Keystone, Breck, Beaver, Vail, A-Basin).

This trip will be in early June. How are the Mosquitos?

Traditionally, June is thought of as buggy season. However, I've NEVER had a really horrible bug experience around here. Also, the higher elevations may not be melted out- there could still be snow in the passes. I snowshoed over Music Pass in the Sangres in June one year. But with this odd snow year that may not be the case. Still might have exciting stream crossings during the melt, though. A couple of years ago the GSDNP rangers refused to give me a permit to hike down the Sand Creek drainage into the park in June because "the stream crossings were too dangerous."

I find this map helpful when looking for a new place to hit in Colorado:

http://www.coloradowilderness.com/wildpages/map.html

Trapper's Lake in Flat Tops Wilderness is about 5.5 hours from DIA (though the eastern trailheads are MUCH closer) so using that as a limit… Indian Peaks or Holy Cross come to mind. As do Collegiate Peaks (bonus for hitting Princeton Hot Springs afterwards). Lost Creek is one of my stomping grounds, but has no peak bagging. Flat Tops itself isn't good for peak bagging, either, though a lot of it is on an 11,000 foot plateau of sorts. And, again, there's Glenwood Hot Springs to recover in.

If you go to Dondo's or Pmag's blogs they have tons of trip reports from the region:

https://dondo1.wordpress.com/
http://www.pmags.com/

Have you considered flying into Colorado Springs instead of Denver? Almost always that's at least a bit more expensive, but it would get you closer to the San Juans, Weminuche, Sangres, etc. (I'm mostly here down south.) Lots of potential easy peak bagging in the Sangres. Heck, you can ridge walk along a good part of it if you're feeling adventurous. Here's a trip report:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=75239

You can bag Conejos Peak (a 13er) pretty easy from a pleasant San Juans hike I did a while ago:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=67107

thanks so much for the post. I'll have to do some research. I love your trip report.