Thanks for bumping this thread - I just finished a trip from Atlanta->Black Hills/Rapid City->Yellowstone->Grand Teton, and it was amazing as well. Anyone who thinks we need less national parks/protected public lands hasn't spent any time in them.
This was an epic 3 week trip in our household - we left Atlanta on a Friday afternoon and drove the 8 hours to St. Louis. Overnighted there and it was another 12 up to Interior, South Dakota (one of the Badlands NP gateway towns). Got in late Saturday night but were at the Badlands first thing Sunday. Spent Sunday at the Badlands/Wall/Minuteman missile site, then headed over to Rapid City which was our home base for 5 nights. From Rapid City we did Custer State Park, Mt. Rushmore, Crazy Horse, the Needles Hwy, Spearfish Canyon, and Deadwood.
Leaving Rapid City we tried to get into Devil's Tower (line was too long to get in) and then headed over the Bighorns to Cody. A couple nights in Cody for the Buffalo Bill Museum and the Cody rodeo. After leaving Cody, we drove up the Chief Joseph Scenic Byway and Beartooth Hwy to Big TImber, where we were at a dude ranch for a week (this was the wife's 40th birthday present).
Leaving the dude ranch a week later, we camped a couple nights in Yellowstone (Mammoth and Slough Creek campgrounds), spent 2 nights in West Yellowstone, then headed down to Grand Teton. Hit all the highlights in Yellowstone - Grand Prismatic via Fairy Falls, Old Faithful, Lamar Valley, Grand Canyon of the Yellowstone, etc, but our favorite park of the trip was Grand Teton. Mormon Row was awesome, and the hike around Jenny Lake was pretty fantastic. Then there was the 24 hour drive home
Strongest recommendation of the trip - the Gypsy app. If you've not heard of it, it's an app for your phone that utilizes your GPS (no data connection required) and is essentially like an in-car tour guide. There is one available for the Black Hills, and a separate one available for Yellowstone/GTNP. This is the best $10 you'll spend on your trip. It tells you stories, gives you facts about landmarks you're about to see/have seen, and recommends hikes and other points of interest. Highly recommend.