There are a lot of approaches you could take to this. You can compare two poems from the same poet, or two poems on the same subject. Let’s take the first approach.
Here are two poems from Robert Frost. The first one is “Fire and Ice” and the second one is “Mending Wall.”
The two poems are very different, but focus on similar themes. In “Fire and Ice” Frost describes the word ending in either fire, or ice. Will the world end in a fiery apocalypse, or will hate kill us? It reminds us that people are destructive.
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.
(You can read the poem here: http://www.poemhunter.com/poem/fire-and-ice/)
People will destroy each other by hating one another. A fiery apocalypse may not take us out; we will take each other out.
In “Mending Wall” Frost again examines the human condition and how people interact. In this poem, two neighbors discuss the reason for having a wall between their properties. The speaker does not think the wall is necessary.
My apple trees will never get across
And eat the cones under his pines, I tell him.
He only says, "Good fences make good neighbours."
The poem addresses the same universal point, that people’s interactions with one another should be based on having things in common and treating one another right, rather than being opposed to one another.
I think you can make some other interesting comparisons between these two poems.