What I like about Gantz is that there is no clear conception of good and bad unlike in many other mangas. Also the characters have flaws in them, which is realistic. Also gantz shows both good and bad qualities of people and that people are capable of changing to a worse or better person. Gantz also has a very unpredictable storyline because a lot of people are introduced and then killed off, which they are then replaced again. That way gantz never gets boring for me.