What Makes a Good Poem?

I only ask. I've just received some poems back from the Rialto that I sent some time ago. I've had 3 poems in the Rialto over the years, though they've always been somewhat odd choices. These poems I sent were amongst my very best, so I thought. I'm pretty sure, when you write a bad poem, that you send things off more in hope than expectation, but when you write a good one, and they are rare, there's an element of greater concern when they get rejected: maybe I know nothing, maybe, this, which is the rare good one, the best I can do, in fact, is still pretty mediocre. I'm not a fan of mediocre poetry in my own work or anyone elses. When you "interrogate" even one of your good poems it tends to fall apart; so hard is the art. Though I think, over time, I'm quite a good judge of my own work, I haven't the luxury of everything (anything) I write being published. I wrote another "good" poem (in my terms) recently and I'm very pleased with it, but also scared... whatever is good in my criteria doesn't necessarily filter through. Already, good poem that it is, I know it's not perfect.. What to do? What to do?