There is a really long history of poetry that recounts historic events that goes back to the ancient world and the roots of Western literature. Epic poetry, for instance, was often historic, and according to the 16th century Italian poet Torquato Tasso, this was a distinguishing difference between epics and romances (by which I mean narrative poetry about adventure or magic like Orlando furioso or The Faerie Queene). Some epic poetry dealt with the distant, mythic past, the Iliad and Aeneid, for instance. There is a large amount of epic poetry that revolves around foundational events in a people's or nation's history, like the Armenian Daredevils of Sassoun or Kalevala. Of course, there's a good question about how much the authors think of these sorts of works as history, and things like the the Daredevils of Sassoun were thought of as more historical than the Kalevala or Aeneid. Other epics described more recent (though still distant) events, like La Chanson de Roland and Tasso's own Gerusalemme liberata. According to Tasso, the proper way to choose an historic event to recount in epic form was that it occurred distant enough in the past that there was an air of mystery and mysticism to it, that no one living could remember it, but that it wasn't so far back that the way people lived was totally foreign to the way people lived in their own time (for reference, his epic was about the First Crusade and was published in 1581). Of course, that was just his opinion and in no way authoritative or accurately describing how other people wrote poems. With these poems, again, how much they should be considered works of history is open to interpretation: Tasso didn't really consider himself to be writing history, while the Chanson de Roland's author might have thought of his work as somewhat accurately recounting an historical event in a somewhat fantastic way. And then there were some that covered more contemporary events as well, the one that jumps most to mind is Os Lusiadas, a Portuguese poem from 1572 about Vasco de Gama's voyage to India seventy-four years earlier.

Beyond epics, people were always writing poetry about the events in their lives. Some were personal poems that vaguely reference historical events, while others were laudatory poems written for patrons that describe their deeds. Panegyric poems were a tradition in a number of cultures, for instance. Louis XIV had court poets who recounted parts of his reign in verse. A lot of poetry described historic events. People who lived through events wrote poetry. Some were vague mentions of events or just were tinged by historic events, see something like Milton's "Captain or Colonel, or Knight in Arms," which is colored by the anarchy and violence of the English Civil War, while others recounted specific events, Christine de Pizan wrote a short poetic history of Joan of Arc.

Generally, if the poem wasn't something written by a person involved in an event, it shouldn't really be read as an historic document. These poems are often read as documents about the time they were written, not the time they're about. Gerusalemme liberata tells us more about 16th century Italian views of the world than it does about the First Crusade. Christine de Pizan, who was a contemporary of Joan of Arc, isn't a great historical source since she wrote the poem based on second or third hand accounts while she was living in a monastery near the end of her life, but it might give us a sense of what people understood to be true about or thought about Joan of Arc while she was alive (though you can't take this too far, since poetry is ultimately a single person's perspective).

And to answer your question, my favorite poem about history is Gerusalemme liberata. It's a beautiful poem and very well crafted. But there are far, far better modern histories of the Crusades, and if you want a first-hand or medieval account, you'd be better served by the Gesta francorum, Foulcher of Chartes's account, or William of Tyre's later 12th century history. That doesn't make it a bad poem, just not at all historic.