Besides being too expensive for HBO at several million an episode, I think part of the reason this show wasn't successful was because it is too thoughtful for mainstream consumption. This has the potential to be one of those things that got swept under the rug at the time, but will continue to have fan writings, conventions, and influence conversation for decades.
I see many things in the show that are familiar themes, good against evil, Ray Bradbury characters, boy as hero, but the episodes themselves are very unique and engaging. I was completely hooked after renting the first two episodes on DVD and immediately bought both seasons to have.
My only warning is that true to any HBO series, there is strong language and lots of sex, so I don't watch it when the kiddies are awake.