Edumund Spenser was (and is) called "the poet's poet" because of the very high quality of his poetry and because he enjoyed "the pure artistry of his craft" so much.  He is also called that because so many other poets thought that he was a great poet.

Some of the great poets who admired him include John Milton (who wrote Paradise Lost), John Dryden, John Keats (perhaps most famous for "Ode on a Grecian Urn") and William Wordsworth (famous for his romantic poetry such as "The World is Too Much with Us").

Much of their praise is for his unfinished masterpiece entitled The Faerie Queene.