What is poetry? The meaning is apparently difficult enough that my dictionary uses circular defining. "The art or work of a poet" is the first entry. The other two definitions don't clarify this much. I might define it as "The use of words in a primarily artistic (as opposed to informational) form."
However you define poetry, a given poem often can't be enjoyed universally. This is because unlike writing that "explains" things, poems use words to evoke scenes and emotions more directly. Words and their connotations are cultural, so as a result most poems don't translate well. (An exception is haiku, which translates better because of it's heavy reliance on simple nouns and verbs). Certainly the concept of "apple pie" and the words "red, white and blue" could evoke more feeling in an American than in someone from Mongolia.
More than just the larger cultural connotations of words, though, is the issue of the personal meaning that words and scenes have for each of us. A line like "Making love by the dashboard lights," from the singer Meatloaf, may be very poetic to some, but meaningless or even offensive to others. It all depends on the experiences of the reader, and the personal meaning attached to the words.
Consider the following stanza from "Their Eyes":
Shame becomes a smaller thing
The first time you reach down
On the side of the road
To pick up a can or a bottle;
Pick it up and put it in your bag
Without hesitation, without waiting...
For traffic to clear.
For some this would be meaningless. For others it would be understandable at least, because they know that in some areas people collect cans and bottles to turn them in for a refund or for the scrap aluminum value, and that the people who do this are looked down on or pitied. Now, for the person who has actually done this, who may have even been homeless and needed to collect cans - that person can relate more deeply to the poem.
Since this is not a widely shared experience, it may not be a poem that can be widely appreciated. On the other hand, writing poetry like this can be very cathartic and meaningful to the writer. It can even help him understand the feelings he has. This is why poetry is often more for the sake of the writer than the reader.
A lost love can be related to by millions. A margarine tub full of blueberries can bring back childhood memories for hundreds of thousands. Maybe a few hundred of us can relate to the sense of peace that comes from collecting blueberries on rocky islands a day from the nearest road. Without further explaining, two shoes on a tree stump might bring just one person to tears, while being meaningless to the rest of the world.
Of course these things can be explained. All experiences can be made more universally understandable in good poetry. However, as with jokes, the impact can be lost with too much explanation. It is wonderful to be able to touch others with your words, but in the end, perhaps the value of a poem starts and ends with its value to the poet.