Putting aside the source material, the movie was just... okay. The dubbing was hurriedness and character development was kind of lacking in some areas. The CGI and the movie props were handled very nicely.
Adapting a very extensive manga like Gantz into a two part feature film, changes are to be expected. So some of the backlash that the film is getting for not following the manga should be a bit more mellowed. But taking into consideration some of the changes they did make, the film could have been better.
Biggest changes made (In my opinion):
-Number of participance in each mission were decreased.
-The Tanaka aliens mission only had one Tanaka alien.
-Kurono is currently job hunting while attending a University.
-Masaru went to juvy for killing his father and his compassion for life is downplayed.
-No brain bombs.
-Kurono's awesome-ness, was no where to be found!
a good 6 out of 10