Abridged Review For People Who Don't Like Reading:
Getter Robo Armageddon is a show about giant robots thrashing the shit out of everything with glorious high quality animation. It could also totally kick Jupiter's ass.
Getter Robo Armageddon - You have to be insane to enjoy this show.
I'm not going to lie to you, the story is awful. It consists of all the typical BS you expect to find in anime and then some. There is incoherent babbling about evolution, a massive explosion that wipes out a good chunk of humanity, the "good guys" saving the Earth from the forces of evil despite the fact that
almost all the Getter pilots are chaotic and insane (which according to the manga is practically a requirement to pilot Getter), some tidbits of SCIENCE which nobody actually cares about, and of course the solution to all of life's problems, which is to have a giant robot and be more awesome. Fortunately the story being so awful is what helps to make it entertaining. How am I supposed to enjoy characters being able to pull guns out of thin air, giant robots duking it out with other giant robots, aliens, or Jupiter, YELLING WHICH IS THE ONLY ACCEPTABLE FORM OF COMMUNICATION BETWEEN MEN BESIDES THEIR FISTS, and explosions when there has to be a good reason for them? Exactly.
There are four types of characters in this show. The first is ordinary people. They are rare and should be kept away from the action unless you want to have to deal with zombies. The second is awesome people. These are most of the people involved in combat, which means most of the cast. The third is evil people. These are people who are easy to distinguish because of their ridiculous laugh and the fact that they won't freakin' die when they're killed. The fourth and final type is Ryoma. When you see Ryoma you know that someone is about to enter a world of pain. In summary, if you're looking for a show where you can't describe basically everyone with the word "badass" and the character development consists of more than a character going from "awesome" to "more awesome" this is not the show you're looking for.
The art in this show is very gritty and '80s anime-ish, except pulled off a lot better than most '80s anime. For the most part it does a great job of staying true to the look of the various installments of the Getter Robo manga done by Go Nagai and Ken Ishikawa, meaning that the robot and character designs range from goofy and childish to tough looking and cool and that there are huge grins and crazy eyes galore. The animation is also surprisingly good. The range of motion is lacking compared to the best of stuff today, but there still tends to be a good amount of motion without the art quality being sacrificed in the progress. Thus it goes without saying that the high quality of the art and animation combined with the crazy mecha action elements makes for one of the best looking mecha shows available, despite the series being over a decade old now.
The soundtrack leaves me with few complaints. Both the opening themes are likable and hot-blooded and the typically rock/metal oriented tracks within the show fit the action well. I wouldn't actually listen to the soundtrack on its own, but the same goes for 99% of soundtracks out there. The voice acting is mostly very good, with everyone clearly knowing that if you aren't going way over the top in a super robot show you aren't doing it right. Dr. Saotome sounds a little too comically evil for my tastes, but then again the show basically turned him into Dr. Hell so I can't really fault his voice actor for that. Other than that I can't think of any problems I had with the voice cast considering everyone fit their roles well as opposed to sounding like they were picked due to their popularity like a lot of stuff nowadays.
According to the credits there were three different directors for this show over the course of the 13 episodes, but the main one was Yasuhiro Geshi who did the 2nd episode and episodes 6-13. Since doing this show he has directed a couple of episodes of GitS:SAC, New Getter Robo episode 8 (one of the best episodes in that great series), and Gurren Lagann episode 20 (Yoko/Yamako-sensei episode). While I wouldn't say his directing in this series was great necessarily, I can say that the guy knows how to direct some exciting action sequences. It certainly didn't hurt that he had a bunch of great animators to work with, but there clearly is a love for the material here that gives the show the type of soul and value that would've been lost had the directors not cared and simply phoned it in.
Of course then the question is raised, did he really direct the 2nd episode and did one of the other credited directors do episodes 1 and 3? This doesn't seem to be the case, or if they did they were solely the episode directors, as initially super robot enthusiast Yasuhiro Imagawa was the main director of the project. Due to some sort of undisclosed disagreement he was taken off the project after episode 3 however, which infuriates some of his fans. While I can agree that Imagawa probably would've helped the story make a lick of sense, I don't think the show would have been any better/worse had he stuck around as the insane action and high quality animation are really the driving force behind the quality of the series.
It really does take a special kind of crazy to be a fan of Getter Robo Armageddon. There is even a screenshot from the series floating around of Ryoma pondering, "What the hell is going on? It doesn't make sense at all!" If you can manage to fit into that mold of insanity even a little however, there is a ton to enjoy here as GRA is one of the most nonsensical, brimming with action, mind blowingly awesome anime series out there. Don't think, feel.