What makes a poem good?

Frankly (though I haven't read this thread all that closely) regarding 'different levels' of literacy or sophistication in understanding all that's going on in a poem, there's no reason why a single poem can't touch on all that.  Meaning the surface of the poem can incorporate all kinds of accesible meanings and technique while still incorporating quite a bit of very interesting allusions and nuance picked up by the keener eye.  In fact, truly excellent poetry often takes that form - layers of meaning and craft that add up to a broader whole without diminishing the immediate appreciation of the poem itself.

All that said, there's so many different tastes in poetry and different techniques to be employed, that it's difficult to ever agree on what makes 'quality' poems.  All I'd be willing to say is that there is a combination of experience (both in reading and writing), self-confidence, original expression, and the ability to strike a chord (in whatever way) that manifests itself in good poetry. I like variety and experimentation - hence, my ideas on something being good are going to vary wildly from someone else with a more specific genre in mind.  To each their own.  Determining a poet's level of craft, though, often means having intimacy with the genre the poet works in.