Are the Gantz movie sequel to the anime series?

Question

Gantz anime isn't finished, but I want to know what's the deal with films.

Are they a sequel to the anime? Do they tell the whole story from manga, or what?

Answer 1

The Gantz film series is indeed based on Hiroya Oku's manga series, Gantz.
However, they are a substantial amount of differences between the movie series and the actual manga. Some of these differences are listed below

Gantz 1

• There are only two aliens in the second mission.
• Kato never went to high school, because he was in Juvenal Hall for killing his abusive father.
• Most characters don't appear at all.
• Tae is chasing after Kurono early on.
• Kurono doesn't start off as a jerk, nor very bad ass at all. Instead he avoids conflict, and acts more as a suit wearing intellectual.
• Kishimoto committed suicide not because of her mother's bullying, but because her boyfriend left her for someone else.
• No mention of second Kishimoto.
• Gantz isn't as rude or interesting.
• When the missions are over, people are teleported to their homes.
• Suzuki joins the team during the first mission.
• During the first mission, Kurono is teleported out, holding his suitcase, and apparently forget that he left it laying on the floor of the room.
• Kurono jump down to help Kato move the drunk off the tracks, but instead reaches for Kato to help him get back up. Somehow Kato pulls him down to him, and they get hit then.
• The hundred point menu does not have the option for a superior weapon, only the options for exiting with a memory loss or reviving someone from the database. When the timer ran out during the Thousand Arms Buddha mission it reset instead of returning them to the room.
• They fought with Thousand Arms Buddha before the Giant Statue Buddha, for some reason he was a tiny figure which grew into a giant statue. No explanation of what happened to Thousand Arms Buddha after he beat the Giant Buddha Statue.

Gantz 2: Perfect Answers

• Thousand Arms Buddha revealed to be a shapeshifter duplicate of Kato.
• Vampires are called Men In Black and not shown to be vampires.
• Akira Kurono is not a vampire.
• Previous Tokyo Gantz Team members are different from Gantz/Minus, except Nishi Reika is replaced by Eriko Ayukawa, who is a previous Gantz team member instead of a new member, and doesn't like Kurono.

Source

Answer 2

The Gantz anime is finished, and it purposely strays from the manga because at the time the manga had way too many bouts of hiatus. (much like Berserk)

however, the Gantz manga has finally and only recently ended (as of 2018) and any CGI or Live Action adaptation has simply been an odd mosh mash telling of parts of the manga with details and characters mixed up.