A great question that should be asked more often. If you read the poem in romantic terms, you might arrive at the following interpretation. The speaker in this poem is tired and bored with his era. The speaker is living during an era that is trapped into a system of values and THINKING that is not as exciting as the era of ancient greece.

Try to compare your life with school, friends, televsion, sports with the life of a boy or girl living in the ancient greek world. The boys and girls of the ancient greek world lived exciting lives filled with music, art, athletics, and love that were connected to the tales of the Greek gods.

An interesting question. The scenes on the urn appear in isolation; life always gets tangled with other things.

The scenes on the urn are perfect; life is not.

The scenes on the urn sum up specific elements of life really well. They are selected and symbolic. Life is not.

Most importantly, the scenes on the urn remain perfect, while life changes.

In what way are the scenes depicted on the urn superior to their real-life counterparts?

The speaker views the scenes depicted on the urn as superior to real life in two ways. Firstly, the scenes are beautiful. They present an idealized look into daily life in the ancient world. In a way, they are more beautiful than real life because of the medium in which they are presented: still images. As the speaker observes when looking at the musician on the urn,

Heard melodies are sweet, but those unheard
Are sweeter.

The spectator can never hear what the musician is playing—he is merely an image. But the music the speaker imagines is likely better than anything the original artist could have come up with.

Secondly, the images on the urn will remain beautiful as long as the urn exists (which the speaker appears to assume will be forever). The young lovers will never grow old. The tree's leaves will never be shed with the coming of fall. Death, too, will remain a stranger to the figures on the urn (an irony, considering that the purpose of an urn is to hold a person's ashes). All will remain as lovely and young as they were the day their creator made them. Unlike in the real world, where time's passing has consequences, art remains unchanged.