A poem is said to be good if it evokes emotions and resonates with the reader in a meaningful way. A good poem can have many different elements that contribute to its effectiveness, including elevated style, rhyme and reason, a regular rhythm, and so on. However, the most important aspect of a good poem is its ability to connect with the reader and convey a message, feeling, or idea that is significant and impactful. Ultimately, whether a poem is considered "good" is subjective and depends on the reader's personal preferences and experiences.