Gantz follows the story of Kei Kurono: a selfish, cocky, and rather porn-obsessed adolescent, and the trials and tribulations he faces in fighting the plethora of aliens that Gantz conjures. At first, this sounds promising. However, it is not until the second half of the 2nd season that the show becomes monotonous: fight alien(s). survive, repeat. fight alien(s), survive, repeat. fight alien(s), survive, repeat. So the repetitive nature of the show becomes too dull and slightly boring to watch.
Until you realise that one of the best things about this anime is the character development in Kei. Don't get me wrong: the change in person does not occur until fairly late. But it feels right and most appropriate for Kei to have evolved under such pernicious circumstances.
Furthermore, to put it frankly, the CGI and overall animation are terrible; at times it felt like you were watching a 2D school-project movie made by an 11-year-old. There are frequent (and repetitive) moments when one character runs and the screen moves but the character almost seemingly stays in the same position, albeit with their legs moving. You'll see what I mean if you were to watch it.
