Great Smoky Mountains is the most visited National Park in the United States. This is due to the proximity of the park to the major metro areas of the Eastern U.S. And it doesn't hurt that it's free to enter.
While there are other National Parks that are perhaps more scenic by landscape standards, this park does have great views, waterfalls and wildlife.
This photo of a mother bear and her cub was taken from inside a vehicle. The black bears were just 50 yards from the road near the John Oliver Cabin. To be that close was a rare encounter to be sure, but visitors stand a good chance to see some deer, wild turkeys, or perhaps a coyote or eagle. Keep in mind that it is illegal to approach wildlife. A telephoto lens is a good solution if you want up-close pictures.
Cades Cove Visitor Center is worth checking out. Some historic log buildings have been preserved and restored, plus you can enter a working grist mill.
East Tennessee can be hot in the summer with temperatures often reaching the high 90's, with high humidity. The park's roadways are often very crowded in the summer and on weekends. But if you can get off the road and onto some of the 800 miles of Smoky Mountain trails, you can find some serenity.