Kidou Senshi Gundam: Dai 08 MS Shoutai

Both series feature characters from opposite sides of a conflict with opposing beliefs coming to terms with each other to survive. In the 08th MS Team, Federation pilot Shiro, a survivor of a Zeon gas attack, works together with Zeon test pilot Aina after they find themselves losing oxygen and without mobile suits after a space battle. In SEED C.E. 73: Stargazer, Natural pilot Sven, who was indoctrinated with anti-coordinator propaganda as a child, is saved by coordinator astronaut Selene McGriff after their mobile suits end up between Earth and Venus during the course of a battle. 

Both shows were directed and heavily influenced by the late Takeyuki Kanda, who worked on Dougram together with Ryosuke Takahashi. The 08th MS Team is well-known for it's realistic approach on war, the insight in the everyday life of the soldiers, the relationships between the characters . Dougram has it all and adds politics, drama as well as battle tactics. The animation is outdated, but Dougram manages to present 75 well-paced episodes, combined with a huge cast and a detailed story. While Gundam 0079 was the first anime to introduce the concept of real robots, Dougram was the first one to combine robots, war and politics into a great series. read more 

Both are excellent "real robot" mecha anime, and share a very intense and "realistic" feel towards the combat depicted. Both have a strong romance subplot, though 08th is minus the high school setting and related wackiness and also bit thinner on the humor. 08th is also a very good series to get into Gundam, it's set in the same universe as the classic Gundam series however it's more of a side story then anything else. 

VOTOMS and Gundam are huge Sunrise franchises, so it is bound to be some similarities. However, I think VOTOMS is most similar to the 08th MS Team, since both anime share the love for gritty and realistic action, making them prime examples of real robot anime. Also, both of them have an 'impossible love' relationship and both are partially inspired by the Vietnam war. 

Both shows are the most realistic portrayal of their respective genres (battle royale for Btooom!, Real Robot for The 08th MS Team), and both shows are the same length. 

Masaoki Endoh composed both shows (08th MS Team for an opening and 5Ds for an opening/insert songs). Though not exactly alike, they are mature enough to cater an older audience for such taste in their respective franchise. 

Both anime focus on the military and the lives of soldiers, having somewhat grounded depictions of futuristic warfare involving mecha. Lots of military combat action scenes on both sides, and an overall similar vibe. 

Both are military anime which focus on a group of commandos sent on a dangerous mission in a secluded area. Both have a semi-realistic depiction of war, with the main different being that Gundam has mecha elements, while Cat Shit One has anthropomorphic animals. Overall, both are action-packed and have a similar atmosphere. 

ATE is said to be CG's version of 08th ms team and is pretty much it's spiritual successor. They take place aside from the main story dealing with a loyal and ruthless soldier who pilots an advanced mecha said to be the strongest of their military to fight against an antagonistic government filled with aristocrats and nobility. Their life begins to change the moment they meet a rich and beautiful girl who hails from a different race changing their point of view. Their team of pilots share in common too with diversity and characteristics once they join. Antagonists of both stories are similar since they are manipulative, evil, and charismatic with twisted noble deeds. Cameos make appearance too from the main series as they get referenced. read more 

Very similar vibe. A future world of high technologies. A motley crew doing their jobs. Art is similar, too. Kinda episodic structure though everything is connected to the main story. Both shows are a good mix of everything: sometimes easy, sometimes serious, some comedy, some romance, some philisophical and moral questions, drama, action, guns, machines. 

Both are Sunrise Mecha series that deal with a romance that crosses faction lines, although said romance doesn't take center stage until about halfway through the series in both cases, and they also feature a lot of character drama and well animated combat.  

In 8th MS Team, you get to see what the One Year War was like on Earth while getting the perspective of the average soldier fighting those battles. In War in the Pocket, you get to see how that same war affects a space colony which has gotten pulled into it, from the perspective of normal people. 

08th MS Team is "real robot" Gundam at its finest, while Aldnoah Zero makes usage of space magic the first several episodes have some great battles of "real robots" going up much more advanced targets. The score by Hiroyuki Sawano makes up for a whole lot of Aldnoah Zero's shortcomings. This is a fun junk food mecha anime.  

These series share a romantic subplot that is intriguing and keeps you interested in the characters. Oh and Mechs,  

Both anime... ...have stupendous animation, taking its time to show how the mobile suits work and how are destroyed. Also modernizing the designs of the original series. ...are short spin-offs of the one year war, in the universal century, depicting a minor front of the larger war, that is notable for the difference in scenario and equipment deployed. ...take a more realistic and gritty aproach to Mobile Suit combat, with emphasis in equipment, tactics and strategy. ...follow characters, and dynamics among them, in both sides of the conflict portraying in a relatable and human way. ...have romantic subplots, albeit managed in different ways. ...have people who are devastated by the consequences and destruction of war, and people who enjoy the fight and think only about winning. ...have nice people in Zeon.  read more 

Both have two sides at war and in the middle of the war the love of two characters who must face each other despite the fact that loving each other gets in the way 

If you like the stories of Romeo and Juliet, GUNDAM: THE 08th MS TEAM may interest you. It's 'Romeo and Juliet with Mechas'. The boy is a Mecha pilot of the army that defends the Earth... and the girl is a soldier from the faction of humans who live in space that attack Earth. They will face an impossible love. It is a spin-off of the Gundam saga so it is not necessary to have seen any other anime from that franchise.  

Both feature heavy action with the use of tactics, great character development, and believable character interactions. 

Both series put a good effort in the realistic portrayal of mecha combat, an are more successful at it more than most other real robot series. 

Mecha, Romance and two strong protagonists, what's not to like? The signature Gundam series shares many themes with RahXephon but can fall a bit more on the "technical side" of robots rather than its romance. However, it's a great watch despite its age. 

If you liked the realistic depictions of soldiers without superpowers and post apocalyptic scenario of Blue Gender, then Gundam: 08th MS Team is a must watch. An interesting conflict with many types of realistic weapons and mecha with a distinguishable romance story makes 08th MS Team a good watch. 

These animes are quite different and have different messaging. Something similar that caught my attention was the main characters Shiro (Gundam) and Lenka(god eater). Both have to gain the respect/trust as leaders of their misfit teammates with problems of their own, by proving themselves competent. Both anime do a good job at this. 

Both have mechas that aren't as godly as most other mecha shows. 

Both anime is centered about a division/squad of mechs in an ongoing war. It's coincident that both divisions share same number - 8. 

Both OVA's are essentially side stories to the original tv series showing the frontline of the war. TheIr also both slightly more realistic than the TV series and focus on more grunt soldiers than powerfull Newtypes or Perfect Soldiers. 

Both stories are based on the Romeo and Juliet narrative. Gundam: The 08th MS Team it's 'Romeo and Juliet with Mechas'. The boy is a Mecha pilot of the army that defends the Earth... and the girl is a soldier from the faction of humans who live in space that attack Earth. They will face an impossible love. (It is a spin-off of the Gundam saga but being an independent story it is not especially necessary to watch any other anime of that franchise)  

*I'll try to be a bit cryptic so as not to spoil those who haven't watched Shingeki. The 08th MS Team contains excellent fights between robotic "titans". Unlike the rest of the series in the franchise these fights do not take place with the robots flying through space but on the ground; an aspect that allows us to see a greater difficulty of the pilots in controlling those titanic machines. - In both there are Guerrilla warfare executed in similar places: Jungle and villages in Gundam / Forests and villages in SnK. 

Other than Gundam Wing and G Gundam which are popular, try out 08th MS Team and to an extent, 0083 Stardust Memory. 08th MS Team too like G Gundam is unique in terms of style and 08th MS Team is ground based whereas G was fighting. Drama, romance, interactions, tone, story twists, and action are both great. More than one Gundam is involved which is a squadron fighting to end the war if you like Gundams. 

Another great Gundam show to add if you only like Wing. 08th MS Team too is a mecha show but on a different scale dealing with ground based war scale other than space. It isn't just about mechas but action pack hand in hand combat and weaponry with bombs, guns, and blades. Character interactions are great especially Shiro Amada and Aina Sahalin as both begins to fall in love and share the same sentiments as the war goes on even to the end. There too is drama which is more than Wing and a much more darker tone.  

Both anime are Mecha and Space type anime where the people are trying to cope with surviving against a certain impending threat. The real similarity comes from certain characters getting isolated in space from their stations trying to survive until help arrives, from which they start developing feelings for one-another; this in turn leads to scenarios which start to affect the plot in major ways.