Gatlinburg was our go-to for family vacations as a kid. I've spent countless hours walking up and down that strip. And even though it's not like it used to be (more franchise-driven and a bit less locally-owned and unique), I still really enjoy it.
Everyone's tips are good, but I'll add a few...
-I still love playing Hillbilly Golf. There are plenty of putt-putt golf options, but Hillbilly Golf allows you to ride an incline up the side of the mountain at the beginning of your round and descend down the hill as you play. Parking can be a challenge, but I still really enjoy it.
-Pancake Pantry gets a lot of love (and a lot of crowds) because it's been popular for decades, but the best breakfast I've had there recently has actually been at Crockett's Breakfast Camp, farther down the Strip. I think word is getting out, because it's getting more popular now itself, but the food has been outstanding.
-As others have said, I could completely ditch Pigeon Forge and be completely fine with it. Having said that, The Old Mill is a great restaurant value if you find yourself over there around lunch/dinner time. Really good food, and HUGE portions (two people can easily split just about every single entree). At the other end of Pigeon Forge, I always enjoy stopping at Apple Barn. I've had good meals there, but I also enjoy just shopping there and picking up some apple butter to take home.