Giant Robo the Animation: Chikyuu ga Seishi Suru Hi

Two works by Imagawa, which share characters, themes and designs. Both have a retro-future aesthetic, and a complex and engaging plot. 

While Giant Robo is a lovingly crafted mix of all the works of Mitsuteru Yokoyama, Tetsujin 28 (2004) is a re-imagining of the manga and beloved 60s anime of the same name. Both share the same director, and his immense talent is on full display in both series. However, while Tetsujin 28 initially seems very similar to Giant Robo (several characters cross over, most notably Murasame Kenji), Tetsujin 28's story goes down a far darker path and is much more grounded as a whole.  

When a powerful new technology is discovered, humanity questions if it will be a tool to help them or a devastating weapon. The protagonist is a suit-wearing child-genius who inherits the burden of controlling the world’s strongest robot from his dead father at a young age. 

Both are retro-styled mecha series based on manga by Mitsuteru Yokoyama directed by Yasuhiro Imagawa that center on many similar ideas, such as historical revisionism, the dangers of scientific progress, sons dealing with the sins of their fathers, melancholic optimism in front of tragedy, and if it's possible for a criminal to redeem himself from his crimes. Due to the unique approach Giant Robo was made with, many Tetsujin 28 characters feature on it, so if you want to see what's basically the closest we're getting to a Giant Robo sequel, Tetsujin 28 is for you. 

Similar style of storytelling. Action-packed yet touching adventures. 

Giant Robo: The Day the Earth Stood Still is, in a sense, the spiritual older brother to TTGL, especially as both involve a young boy's journey to manhood. It has the same wow factor, however Giant Robo conveys a greater depth of heroic nobility and cunning villainy, and the action is more over-the-top than TTGL, especially as most of it is hand-to-hand. When you see the Big Bang Punch you'll understand what I mean. 

Bombastic, exaggerated, ensemble action featuring giant robots. Themes of succession and the topic of sustainable energy abound, and the general character dynamic of a kid having power over a bunch of doubtful adults are shared. 

Both of them are insane "WHAT THE HELL IS GOING ON" for the first episode, and they have the same director. 

Over-the-top and retro mecha shows directed by Yasuhiro Imagawa. Both are revivals of classic series, but discard the old continuity to tell an all-new story that can be enjoyed by both old and new viewers. They're also huge tributes to the careers of the original creators, featuring characters and plotlines from the original creator's entire body of work. However, it's not necessary to be familiar with the source material to enjoy them. 

Shares the same director, Imagawa. Both shows contain humans with superpowers, and both have plenty of plot twists. While Giant Robo was imagawa's take yokoyama's works, Shin Mazinger is imagawa's take on nagai's works. 

If you liked the ridiculously over-the-top, over-dramatic kung fu super robot fighting action of G Gundam (and if you didn't, I don't know what to say to you), Giant Robo: The Day the Earth Stood Still does it better than anybody. Much like G Gundam, Giant Robo combines a grand, sweeping martial-artsy storyline with larger-than-life characters, but while G Gundam feels like a (very awesome) Saturday morning cartoon, Giant Robo feels like an opera, with an amazing orchestrated score and long speeches that feel more like arias. 

Unusual mecha, nice typical 90's animation and designs that are based on the nationalities of the characters. 

Both are very good steampunk shows that require at least one viewing. The robots both have a similar kind of design and mass as well. 

The Big O has so much references to Giant Robo, that you could think that they are both set in same universe. Actually, this is pretty good explanation for... oh, wait, no spoilers. But the atmosphere is completely different: Giant Robo has a classical "superheroic" plot, and The Big O is very close to noir drama. 

Remote controlled robots. Also, both Giant Robo OVA and Heroman have excellent animation.