Not sure what you consider epic but I enjoy views and those are hard to come by in the Smokies as you're normally surrounded by trees/brush. My favorite loop so far was AT from Clingman's Dome to Siler's Bald. Then I went down Hazel Creek a ways to check out cascades and such, then back up and over Jonas Creek and then up Forney Creek taking the side trip to Andrews Bald (which is quite nice).
I also really liked the out and back to Chimney Tops (open only Fri-Sun this year).
Many people talk about Mt LeConte and Alum Cave trail but it's not a loop.
My youngest (almost 6 at the time) and I did a Big Creek loop 2 summers ago and it was OK. Went up Big Creek to 37. Up Gunter Fork, which took forever because it was officially closed and overgrown. No views but the falls/slide is nice. Stayed at Laurel Gap. Then Mt Sterling and Baxter Creek trails (decided to not stay at 38 to get out earlier). Fire tower is nice if you have a sunny day.
Last summer I hiked up to My Cammerer and back to Cosby to see the view and it was nice, but the trail again had no views.
What I do like about the Smokies are the creeks, cascades and falls.
Personally a more epic trip to me would be the Grayson Highlands. My youngest and I did that one last summer. You're not surrounded by trees most of the time and the wild ponies are cool.
If you check my profile, the link goes to my video trip reports.