That is indeed a great poem. 
The ending to the Akallabeth from Tolkein’s Silmarillion:
It reminds me of how writing and poetry should be: building up and referencing everything in the text before it as well as a perfect sense of rhythm even in prose.
In second place, I’d vote for Churchill’s “Never Surrender” speech or Kings “I have a Dream” speech. It says something about my love of poetry that I think these three choices are the most poetic things ever created even though they are not technically poetry.
ETA: which is not to say that those lines from Ozymadias are not great. But it does have just as much impact out of context as reading the entire poem.
I was going to suggest the 23rd psalm as well, and I’m an atheist . . . looks like that ground’s been covered :).
So I’m left with
We would rather be ruined than changed,
We would rather die in our dread
Than climb the cross of the moment
And let our illusions die.
— W. H. Auden
and this:
It is not the critic who counts; not the man who points out how the strong man stumbled, or where the doer of deeds could have done better. The credit belongs to the man who is actually in the arena; whose face is marred by dust and sweat and blood; who strives valiantly; who errs and comes short again and again; who knows the great enthusiasm, the great devotions, and spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement; and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who know neither victory nor defeat.
– Theodore Roosevelt
and this:
The apple of discord is now fairly in our midst, and if not nipped in the bud it will burst forth in a conflagration which will deluge society in an earthquake of bloody apprehension.
– Nebraska newspaper editorial, circa 1870
Another favorite, full of useful imagry, is Yeats - The Second Coming:
Just a fragment, and it needs the context of the preceding story, but I’m fond of the last part of the last line of Clarke’s The Nine Billion Names of God
“. . . overhead, without any fuss, the stars were going out.”
I have to say both Shakespeare passages made the hair on my arms and neck stand straight up. Lots of other beauties here- Churchill’s speeches taken with their historical context are also very moving. My contribution is from Tennyson’s Ulysses- not the greatest poem ever by any means but the end passage gives me the chills:
you and I are old;
Old age hath yet his honor and his toil.
Death closes all; but something ere the end,
Some work of noble note, may yet be done,
Not unbecoming men that strove with Gods.
The lights begin to twinkle from the rocks;
The long day wanes; the slow moon climbs; the deep
Moans round with many voices. Come, my friends.
‘Tis not too late to seek a newer world.
Push off, and sitting well in order smite
The sounding furrows; for my purpose holds
To sail beyond the sunset, and the baths
Of all the western stars, until I die.
It may be that the gulfs will wash us down;
It may be we shall touch the Happy Isles,
And see the great Achilles, whom we knew.
Tho’ much is taken, much abides; and tho’
We are not now that strength which in old days
Moved earth and heaven, that which we are, we are,–
One equal temper of heroic hearts,
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.
I’ve always loved the quote from “The Dead” mentioned on page one (and would have chosen it had I arrived earlier), but this is great, too.
Hunter Thompson-The Wave Speach.
When Hunter was on…nobody wrote better.
This thread made me cry.
Suffering and tragedy and folly will not disappear in a purified world. They are a part of humanity. That is why, even in a world of suffering, there can also be joy and shining light.
-Hayao Miyazaki
Do you mean the whole poem, or just that stanza?
For some reason, this week, these verses have been going through my mind:
Weave a circle round him thrice,
And Close your eyes with holy dread,
For he on honeydew hath fed,
And drunk the milk of Paradise.
Heh–I often sing the 2 preceding lines in MY head:
Jack Kerouac, from On The Road: “The only people for me are the mad ones, the ones who are mad to live, mad to talk, mad to be saved, desirous of everything at the same time, the ones who never yawn or say a commonplace thing, but burn, burn, burn, like fabulous yellow roman candles exploding like spiders across the stars and in the middle you see the blue centerlight pop and everybody goes "Awww!”
Written by Eric Bachman of Crooked Fingers, this is an excerpt from the song “Sad Love”:
"When you cut the cord to close the curtain on the sun
And evening came to cover everything you left undone
I took a walk out to greet an old familiar ghost
To take a seat among the freaks and watch the red lights glow
On the day you came I swear I felt so drunk
Stumbling I tried to bring you down to where I’d sunk
But throwing a spark you lit up the dark to heat the hateful glow
And burned a bright resentful ring around our sad sad love
Sad love is calling you
What’s meant to be has fallen through
Is running through your veins
An evil kind of bloodless pain
Is creeping through the cracks that swell
To swallow you up into Hell
To shatter all that you believed
And let your lonesome heart be free
So shut your angry eyes cause there ain’t nothing here to see
It’s sad enough they called the bluff on all these lying dreams
That creep through the night where even the slightest defect is exposed
To leave us only half asleep so we can watch the curtain close"
My favorite Henry V passage my not be the greatest moment in literature but it is some eloquent cold blooded shit to say to someone before a beat down. I keep waiting for my ‘Jules moment’ but I guess I’ll have to become a hitman first.
And tell the pleasant prince this mock of his
Hath turn’d his balls to gun-stones; and his soul
Shall stand sore charged for the wasteful vengeance
That shall fly with them: for many a thousand widows
Shall this his mock mock out of their dear husbands;
Mock mothers from their sons, mock castles down;
And some are yet ungotten and unborn
That shall have cause to curse the Dauphin’s scorn.
But this lies all within the will of God,
To whom I do appeal; and in whose name
Tell you the Dauphin I am coming on,
To venge me as I may and to put forth
My rightful hand in a well-hallow’d cause.
So get you hence in peace; and tell the Dauphin
His jest will savour but of shallow wit,
When thousands weep more than did laugh at it.
Thanks for this thread, I’m loving it!
I’d like to contribute the following;
“Just because you’re naked, doesn’t mean you’re sexy.
Just because you’re cynical, doesn’t mean you’re cool.
You may tell the greatest lies, and wear a brilliant disguise,
But you can’t escape the eyes of the ones who look right through you.
In the end, what will prevail, is your passion not your tale,
for love is the holy grail, even in cognito.
So better listen to me sister, and pay close attention mister,
It’s very good to play the game, amuse the gods, avoid the pain.
But don’t trust fortune don’t trust fame,
Your real self doesn’t know your name,
And, in this, we’re all the same,
We’re all incognito.” Tom Robbins, Incognito
And another,
“I believe that imagination is stronger than knowledge.
That myth is more potent than history.
That dreams are more powerful than facts.
That hopes always triumphs over experience.
That laughter is the only cure for grief.
And I believe that love is stronger than death.” Robert Fulghum, The Storytellers Creed.
“Your life and my life flow into each other as wave flows into wave. And, unless there is peace and joy and freedom for you, there can be no real peace or joy or freedom for me. To see reality – not as we expect it to be, but as it is – is to see that unless we live for each other, and in and through each other, we do not really live very satisfactorily. That there can be life only where there really is, in just this sense, love.” Frederick Buechner, The Magnificent Defeat.
For some reason my mind always conflates this …
In Xanadu did Kubla Khan
A stately dome Decree
He crawled upon the railroad tracks
The train he did not see.
Oooey Kubla!
One of Nietzsche’s letters to his sister always struck me as beautiful and powerful:
Woah, that must hurt. 
Reading this thread just now has been wonderful. I was going to mention one of the Gandalf quotes, or something from a favorite poem, but instead I’m offering this little bit of writing I saw in an exhibit once long ago and which has stuck in my mind ever since:
“Something began me that had no beginning; something will end me that has no end.”