It's really hard to compare the flavor of lotus root to anything. I can think of a couple of things that are similar, but then you'd have had to taste those as well. The closest thing that I can think of is taro root, but then you'd have had to have tried taro root. Jicama is the second closest thing that I can think of, but jicama lacks that subtle earthiness and is less fibrous in texture than lotus root.
"Boldness has genius, power, and magic in it."
Johann Wolfgang Von Goethe