As a nurse I see belly buttons everyday at work. I can tell you that they come in all shapes and sizes and that "best" is purely subjective. With those pictured above, it's faster for me to tell you which ones DON'T look real (too smooth/plastic): 6, 7 and 14 All the others are styles of belly buttons that I've seen.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi