I bet that the most important thing which usually appeals to a reader is a connection between a reader and a writer so that it means that reader percieves a content better if it is written from the first person point of view. I am actually talking about a lyric poem as it always contents beatiful language that sweetly seeps through readers mind, making it feel the same thing as the author. Another two forms of poetry also have theis advantages, but I would say that concrete poem is quite complicated and haiku is simple at some point.
