Other qualities I noticed recurrent in great poetry are strong start lines & end lines. You always wanna hook a reader with that 1st image or phrase, & leave them with a reverberating gong of an image at end. Rare is the poem of any real worth that cannot be judged by the mnemonic quality of it start & end lines. And scattered amid those antipodes will be other memorable words, phrases, metaphors to draw a reader along. Ask yourself- how often will you recall a poem not by its title but its main metaphor, phrase, or image: "That Frost poem- "miles to go....'?", "That poem on a girl in a dentist's office?", "That poem on a jar?".... These are the things that go into greatness, like velcro hooks they cranny into the mind & annoy, delight, puzzle, & soothe. But why?