My favorite poem would not be considered one of the greatest, classic, pieces of all time; but I love it. It is, "Children Learn What They Live" by Dorothy Law Nolte.
Anyone who has a child or plans to have a child should read this poem because, in a simple and yet all encompassing way, Ms. Nolte manages to address how positive and negative behaviors of parents can affect a child. The poem sends a beautiful and simple message about children while also evoking some sense of "eerie sadness", as the reader considers the child who lives with some of the negative behaviors in some parents.
While not the most complicated or sophisticated of poems, "Children Learn What They Live" is simple, powerful, and beautiful.