I came across the list in Malcolm Gladwell's excellent new article in the New Yorker about creativity and how it is foolhardy to assume that it always comes from the young. Even if you are not a particular fan of poetry, the best of any genre is bound to be excellent.
1) Prufrock, T.S. Elliot.
2) Skunk Hour, Robert Lowell.
3) Stopping by Woods on a Snowy Evening, Robert Frost.
4) Red Wheelbarrow, William Carlos Williams.
5) The Fish, Elizabeth Bishop
6) The River Merchant's Wife, Ezra Pound.
7) Daddy, Sylvia Plath
8) In a Station of the Metro, Ezra Pound.
9) Mending Wall, Robert Frost.
10) The Snow Man, Wallace Stevens
11) The Dance, William Carlos Williams.
This list was compiled by economist David Galenson, by looking through 47 major poetry anthologies and counting which poems appeared most often. This is a nice, objective way of determining whether a poem has stood the test of time, but it is possible that some poems have stayed around just because of status--Carlos Williams, I'm looking at you. Not that it matters, but my favorite poem for some time now has been Stevie Smith's "Not Waving but Drowning."