What makes a poem good?

Alcuin, I'm afraid this is one of those rare occasions where I actually disagree with you (at least I think I do).  You see, when I write poetry I don't write it for poets to read, I write it in the hope that someone who's never picked up a book of poetry will find himself surprised that it might be for them after all.  In that regard, I think a great poem should speak to the semi-literates as well as the great bereted literati.  Most of my own favourite poems were, after all, written in the bardic tradition and those who knew them probably couldn't do more than scratch an X for their names. 

All poetry is, of course, subjective.  Rene is perfectly right to say that what moves one will not move another.  Personally, I hate both Eliot and Cummings (I refuse to do the pretentious small c thing).  Many would flay me alive for voicing such a thing.  I also dislike, with passion, Ogden Nash.  But the poetry I enjoy will not be enjoyed at all by many others (Mr Of York is not a Rimbaud fan, I believe).   

So perhaps I should qualify and say that the definition of great poetry doesn't change, but its application varies from reader to reader, and if a consensus is ever reached then I think it's time for the lot of us to give in, because on that day it truly will be a dead art.