Most under-appreciated song of the last 100 years?

My choice is…

“Smile” was written by Charlie Chaplin, most famously sung by Nat King Cole,
and was the favorite song of Michael Jackson who knew a thing or two about music.

Smile though your heart is aching
Smile even though it’s breaking.
When there are clouds in the sky
you’ll get by.
If you smile through your fear and sorrow
Smile and maybe tomorrow
You’ll see the sun come shining through
For you.
Light up your face with gladness,
Hide every trace of sadness.
Although a tear may be ever so near

Mother Teresa was known for saying that what the world’s neediest want most is a smile.