Ozymandias

In 1817, Shelley had a sonnet-writing competition with his friend Horace Smith (and a number of others); there had been a recent announcement by the British Museum of the acquisition of a large statue of Rameses II, and that seems to have inspired the idea to use a passage about Ozymandias (a Greek name for Rameses) in Diodorus Siculus's Bibliotheca Historica 1.47 about a giant statue of him and its boasting inscription:

And it is not merely for its size that this work merits approbation, but it is also marvellous by reason of its artistic quality and excellent because of the nature of the stone, since in a block of so great a size there is not a single crack or blemish to be seen. The inscription upon it runs: "King of Kings am I, Osymandyas. If anyone would know how great I am and where I lie, let him surpass one of my works."

Shelley's sonnet was published in 1818 in The Examiner, under the pseudonym 'Glirastes':

Ozymandias
by Percy Bysshe Shelley

I met a traveller from an antique land
Who said: "Two vast and trunkless legs of stone
Stand in the desert. Near them on the sand,
Half sunk, a shattered visage lies, whose frown
And wrinkled lip and sneer of cold command
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them and the heart that fed.
And on the pedestal these words appear:
`My name is Ozymandias, King of Kings:
Look on my works, ye mighty, and despair!'
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare,
The lone and level sands stretch far away".

Smith's sonnet was also published in The Examiner, a few weeks later.

Ozymandias
On a Stupendous Leg of Granite, Discovered Standing by Itself in the Deserts of Egypt, with the Inscription Inserted Below
by Horace Smith

In Egypt's sandy silence, all alone,
Stands a gigantic Leg, which far off throws
The only shadow that the Desert knows.
"I am great Ozymandias," saith the stone,
"The King of kings: this mighty city shows
The wonders of my hand." The city's gone!
Naught but the leg remaining to disclose
The sight of that forgotten Babylon.
We wonder, and some hunter may express
Wonder like ours, when through the wilderness
Where London stood, holding the wolf in chase,
He meets some fragment huge, and stops to guess
What wonderful, but unrecorded, race
Once dwelt in that annihilated place.

There is no question that Shelley's is the greater sonnet -- it has a better build-up and a more flexible use of language -- but it is not a failing for a sonnet to be less good than one of the greatest sonnets ever written, and the last half of Smith's is excellent.