This really should have worked. It had the perfect setting for a gore/violence anime. Unfortunately not every labyrinth has a way out and Gantz got lost.
The story, although being just below average, did a decent job of creating a background for the action. It had some good points, where I got kinda attached to some of the cast, but not to the extent of what Elfen Lied did.
Unfortunately the action that should have followed the story went missing. Fighting sequences in Gantz are like watching a turn-based strategy. Or two amateurs playing a chess game, both taking their time just because they are supposed to, not coming up with anything at all. The other major issue I had with the action in Gantz are those inconsistent enemies. There are moments when they are incredibly strong and then for no apparent reason they are hopelessly weak.
Visuals are average, lacking some variety here and there, but it is enough for some aww gory moments. On the other hand, I wasn't especially sympathizing with those characters, maybe because they were already dead?
I started Gantz seeing all the recommendations from Elfen Lied, Berserk and Claymore and I was a bit disappointed. I just think Gantz didn't achieve what it has set out to do. I like the op though. ;)