Good poetry "hits different". Basically, it innovates and presents new similes, allegories and expressions that have peak emotional impact, meaning, the words are carefully chosen to create the highest amount of emotional resonance. Also, clichés cannot be present. It has to surprise the reader. If I say: "sky blue". That's bad poetry, because it's boring and predictable. If I say "skype blue" it is more memorable, since nobody before has ever used that before and it stands out. There is also the question of cadence. Basically, you will recognize good poetry when you see it due to how it resonates with your neural pathways related to speech and language centers.