A good poem doesn't need to be pretty. It doesn't need a package or gesture, a good poem is in and of itself enough.
A good poem doesn't need technique, it doesn't need figure of speech or linguistic devices or familiar phrases.
It can be one word in length or span pages. It can rhyme or not.
Good poetry is not bound to diction, meter, grammar, spelling, or language itself. A good poem needs feeling.
It is this feeling that makes it art. It is this feeling that makes it true. A good poem is one that lives in spite of language. It preserves feeling where language fails.
A good poem is a vehicle by which a feeling travels from the soul of one to the soul of any that it comes in contact with. That is how you know it's good.