We've been on the road full time (in the RV) since September 2009, so with respect to North American travels, the only bucket list thing we missed is Banff and Jasper, which was once scheduled, but got cancelled by fire season. And I suppose that's not a fair answer, as it's in Canada!
However, I would like to offer some thoughts on travel in the southwest, most especially the Colorado Plateau. This is a good place to learn: https://www.nps.gov/articles/coloradoplateaus.htm
@BigMike: Please, please, please do some Google mapping of your thoughts. Distances are far greater than people realize, speed limits often lower, and whizzing past the scenery is criminal! Flying into Denver will get you to Rocky Mountain NP, which is on your list. Flying into Las Vegas, a two hour drive from Zion NP, can get you started on a loop that includes many places on the Colorado Plateau. In spring of 2013 we did a drive that included Zion, Bryce Canyon, Capitol Reef, Colorado National Monument, Canyonlands, and Arches. That took us a month. Okay, you could do it in less, but we had plenty of time. Travel between Bryce and Capitol Reef is via Utah 12, one of our most stunning byways. We then headed to Mesa Verde NP for the Memorial Day holiday weekend. But, should one desire a loop, one could dip down into northern Arizona and its wonders, such as Monument Valley on Navajo lands and Grand Canyon NP, returning to Las Vegas, or if open jaw is an option, departing out of Phoenix. Additionally, flying into Salt Lake City could work as well. Each time we've gone to Yellowstone/Grand Teton we spent weeks there, in just those two NPs. So just a few somewhat disjointed thoughts....... National Geographic's Guide to the National Parks (we have both US and Canada editions) is my favorite place to start with respect to NP research.
Oh, and one of my favorite place names is Big Bone Lick State Park, in Kentucky. Somehow every time we drive I-75 it cracks me up.
Donna