I agree with what many reviewers said and I wont rehash the story line anymore - many folks have done so already.
What I'd like to add is that HBO Cable Networks did a wonderful thing in showing this as a weekly series. I was glued to the television weekly at midnight - not just me but all of my friends as well. I don't care what I was doing, I HAD to watch this. We all loved this animated working of Spawn. The animation was crisp, the storytelling was adult and intelligent, the vocal casting was superb. This is what adult animation and comic book adaptation was about. The first season was better than the second one to me but both were groundbreaking.
What I disliked more than anything -- was the feature film of "Spawn". It did not hold a candle to this series and just ruined what was already done. Sad thing, HBO hasn't re-shown repeats of this and they should. And HBO hasn't produced & adapted other comics, which it should be doing along these lines. There are many production lessons here as well as a great adaptation lesson.
Todd MacFarlane's creation is the best here. I hope they show it again, release a DVD if so, do not miss this. Be forewarned - adult themes run through this version. The first season is NOT for the kiddies or a PG-13 oriented. It is dark, it is wonderful and it is the world of Spawn as it should be seen and interpreted.