Smoky mountains, colorado, grand tetons (very beautiful by the way). Haven't been to the other two but I'm planning to go real soon and likely this year. Of the three, I've only driven through the grand tetons and that was amazing. So glad it was still daytime. The whole group was all in awe. Grand Tetons are not far from Utah but might be a bit out of the way for you. Liked the sight of driving through there and it was an awesome way to end the trip. Yellowstone was nice too though not quite as beautiful. You could easily spend a couple days just driving around it.
Left Yellowstone and decided to pass through the Grand Tetons to head back to the Utah mountains just as the sun was going down and it was like Ohh...My...but I was driving so it was a struggle to keep my eyes on the road, lol. Plus, being the driver, my view wasn't the best...that was one time where I wished I wasn't, lol. It was still beautiful though. Can only imagine what it would have been like if we managed a hike or two through there...
If you decide to head to Yellowstone from Utah take that route. Went through Idaho to get there and it was nothing but greenish brown pastures, farmland, cattle, and the deep rich aroma of manure in the morning. Won't be doing that anytime soon, matter-of-fact if I never see Idaho again, I couldn't be any happier. Nothing against anyone from Idaho of course. [emoji4]