After trying to rescue a man on the subway tracks, two teens wake up in a room dominated by a mysterious black sphere that sends them to hunt down and kill aliens hiding on Earth. –IMDb
Bad. If you don't know the original work i guess you'll find it badly acted, confusing, uninteresting, barely entertaining. If you know the original , you'll be quite "disappointed". The producers and director just wanted to show the more missions as possible, 3 in 2 hours it's too short. No time to develop the characters, and their relationships, no time for background, no time for extra characters (lots are missing)
Like "Death Note," this is a lengthy, two-part live action adaptation of a popular manga/anime. Unlike "Death Note," "Gantz" treads more into pure sci-fi territory, combining elements of "The Matrix" and "Men in Black." The movie version wisely tones down the more "ecchi" (sexual) elements of the anime but keeps the blood 'n gore intact. Overall, I was thoroughly entertained and look forward to Part II.