In Getter Robo Armageddon, Shin Getter is Professor Saotome's ultimate creation during the prologue of the story. After breaking through a group of mass-produced Getter Robo Gs, Ryoma Nagare and Hayato Jin find it inside the Saotome Laboratory along with Go "Saotome", the professor's genetically engineered "son". When the trio learns that the military has launched a nuclear warhead at the newly-formed Shin Dragon, they use Shin Getter in an attempt to stop the attack, but ultimately fail, causing a Getter Ray contamination that kills most of the planet's population. Several years later, when the story picks up again, Shin Getter is piloted by Go, Kei Kuruma (Getter teammate Benkei Kuruma's adopted daughter) and Gai. They use Shin Getter until Shin Dragon joins them willingly to fight the Invaders, at which point Ryoma, Hayato and Benkei take up the piloting duties for Shin Getter. The two Getters combine their energy to create incredible attacks, capable of destroying Jupiter and its Invader-infected moons, but Shin Getter ends up stranded in another dimension, fighting alongside Getters from other universes for all eternity. (Wikipedia)

Getter Robo G (ゲッターロボG - Gettâ Robo Jî) is a Super Robot anime series created by Go Nagai and Ken Ishikawa and produced by Toei Animation. This direct sequel to Getter Robo was broadcast on NET (now TV Asahi) from May 15, 1975 to March 25, 1976, with a total of 39 episodes (some episodes were rebroadcast, erroneously giving the impression that there were 43 episodes).

People familiar with Mattel's popular Shogun Warriors toy collection will remember all three of Getter Robo G's robot formations in that toy line: Getter Dragon (Dragun), Getter Liger (Raider) and Getter Poseidon (Poseidon). As a result of the popularity of these toys in the US, Jim Terry included this series in his Force Five anime lineup under the title of Starvengers. The original Getter Robo series, however, has yet to appear in the US. (Wikipedia)

After some years, the franchise was revived in 1991 with the new series Getter Robo Go, directed by Yoshiki Shibata, and featuring a new robot and an all-new team. Despite lasting 50 episodes, it was considered a noncanonical flop. Nevertheless, the manga of Getter Go is considered one of Ken Ishikawa's best works, featuring the Shin Getter Robo for the first time. The OVA remakes use a lot of ideas, characters and situations from Getter Go manga.

Despite this, the influence and popularity of the original show continued in Japan, and it found a way to stay with fans through video games (like the Super Robot Wars game series, in which the Getter Robo is one of its lineup mainstays) and other merchandise. The series was even spoofed successfully in the mecha anime series Martian Successor Nadesico, where the anime-within-anime Gekigangar III was a direct pun (and homage) to the Getter Robo legacy, among many other super robot series.

Shin Getter Robo (真ゲッターロボ) (usually called Shin Getter for short) was created by Banpresto for Super Robot Wars 4, a game released for the Super Famicon (also known as the Super Nintendo) game console. The concept was to give the Getter team a stronger machine for later stages of the game. Banpresto contacted Go Nagai and pitched the idea to him, and he agreed to come up with the new machine. Nagai liked the design so much that he adopted it into multiple Getter Robo universes' storylines.

Shin Getter Robo vs Neo Getter Robo (真ゲッターロボ対ネオゲッターロボ) is an anime OVA series based off the works of Go Nagai. It was released in four episodes on four DVDs from December 2000 to June 2001.

Shin Getter Robo vs Neo Getter Robo draws heavily from Nagai's manga Getter Robo Go. An anime adaptation of Getter Robo Go was made in 1991, but was toned down, losing most of Nagai's famous style. Neo Getter Robo features much more faithful versions of Nagai's characters, but with a new plot and new Getter. Because of this, many consider Neo Getter Robo to be a redemption for the Getter Robo Go anime. (Wikipedia)