What makes a poem good?

Interesting that you should say "writing at different levels" -- and although I don't think one has to dumb down or really alter too much, it is true that certain themes and ideas are only going to appeal to the more literate because they're the only ones who've read what you're referring to.  I do believe that certain poems can be used as stepping stones to more "advanced" poetry -- that, as I see it, is our job.  If we can't attract new blood, then it's doom and gloom I'm afraid.