Captain Earth

Produced by Studio Bones, Star Driver and Captain Earth are mecha series with style. But more than that, there are also mysterious origins relating to the world both series are part of. In essence, there are strange phenomenons involving the main protagonists as they deal with mysterious factions. There is decent amount of action, drama, and focus on the conflict between various characters. If you're looking for a mecha show with similar style, these two titles should be under your radar. 

The protagonist Daichi has a similar background to Renton as they both are young boys who are not satisfied with the current life they lead and want to pursue something they love and feel passionate about. Their fathers are both intertwined in a series of strange circumstances surrounding the causes of their deaths. They also both share a strange connection with a young girl who seems to have special abilities and shrouded with an air of mystery.  

Although far more lighthearted, there are several echoes of Neon Genesis Evangelion throughout Captain Earth, this is probably a result of Yoji Enokido working on both series. In terms of plot; both series are about an organization vowed to defend the Earth; NERV fights Angels and Globe fights the Klltgang. However, both of them have overseeing organizations pulling the strings; SEELE and Salty Dog respectively. In terms of characters; The protagonists; Daichi, Akari, Teppei and Hana parallel Shinji, Asuka, Rei and Mari, respectively, they all share a house together under the guidance of Commander Nishikubo just as the protagonists of Neon Genesis Evangelion live with Misato. Daichi is more competent than Shinji is. Daichi was "chosen" by the Livlaster gun to pilot the Earth Engine and Shinji is the only one that can Eva-01. However Daichi continues to fight by choice knowing he has this power, Shinji is forced to. Shinji is also directly influenced by his father whereas Daichi is surrounded by the story of how his father saved the world. Akari fills the role of Asuka but their personalities are strikingly different. Akari is a highly intelligent hacker with an upbeat personality and magical girl motif with a parodic tragic past. Asuka, on the other hand, is the classic hotblooded and aggressive mecha pilot with a tragic past. Teppei is essentially a male Rei clone, their personalities are very much a like and Teppei even shares a similar character design; red eyes and bluish hair. He also has prior connections to the antagonists and is subject to experimentation like Rei. read more 

Both titles involve a sort of boy meets girl, girl has alien origins, boy attempts to rescue girl, secret government stuff, and... You'll have to watch for yourself, I'm not spoiling any more. 

Captain Earth and Aldnoah.Zero are similar in a way because they have a team fighting against people that live in space and also the plot and the character development are the quite same too  

Both are more lighthearted mecha series than its contemporaries and have MC's that both have a vague memory. Both MC's are also thrown into a world where they have to fight off the opposing faction in super giant robot battles that leave minimal damage to the actual planet. Both also have a mostly teenage cast.  

It's the show all the stuff from Captain Earth that was good is originally from. Also try Evangelion! 

Captain Earth and Majestic Prince have similar content in it's story and genre, like a Mecha action, and aliens invading a human planet. The antagonist are mostly an alien species that are invading a human planet with their reasons and the protagonist, mostly a group, or teamwork, will prevent them from conquering the planet. They clash between each other, and have a wide variety of weapon armaments that gives them the upper hand to defeat one another.  

It has a similar vibe to it. The MC has an accident or some sort of reason not to pilot the mech. It has a similar cast of high school boys and girls and has a "reason" that these teenagers are the only one to fly these mechs. They both have to fight some foreign power from another plant or different species or robots or whatever.  

Similarity : + Transformable mecha units + Mecha unit in both anime is not single unit but consists of 3 parts (Head-Body-Legs) + Main enemy is something like "alien" + MC fighting not alone but in teamwork Different : + Aquarion is not controlled by one pilot but 3 pilots simultaneously connected there mind and body into a single coordination NOTE : Both anime is really good for super sentai fans (power rangers in west) 

Captain Earth is a super robot show and the way Studio Bones has beautifully animated the mecha in this series really brings back memories to the 2 dimensional era of the 90s such as the best of them all; King of Braves GaoGaiGar. The Earth Engine's combination sequence gives the same pleasure as GaoGaiGar's. The plot of Captain Earth is very similar. Just as the international organization, the GGG, use robots to protect the Earth from the Zonders; shapeshifting aliens that can take the form of robots, humans and other objects, Globe uses Impacters to protect the Earth from the Kiltgang, aliens that can take the form of humans and robots called Planetary Gears. The Impacters from Captain Earth are administered from a mission control headquarters just like the robots in King of Braves GaoGaiGar are and gives a very similar feeling. One can really relate to the characters of Captain Earth but all the same, they provide a lot of fun as the characters of King of Braves GaoGaiGar do. read more 

both are mecha, the protagonists are both weak (at first anyway) and both protects Earth. 

In both anime, because of incidents/encounters, a normal male high school student becomes involved in a war between humanity and an alien race from somewhere in space. Both anime feature many mech battles along with other powers and abilities that are used in combat. 

It's all there; the young boy recruited by the organization protecting earth to pilot a mecha only he can operate, the alien invaders threatening the planet with their own strange mecha, the renegade alien helping the humans, the tropical island setting, the xenophobia, the singing, the traitorous superior working against the lead 

- Mecha unit in both anime is not single unit but consists of several parts - Although consisting of several parts, there are units that can fight individually (Earth Engine Ordinary & Nova Angel Humanoid Mode) - The main character is composed of one group consisting from 4 members (Mid-Summer Knight & Team D) IMO, If you like Super Sentai Series (Power Ranger in west) you will be like this