Ryuugajou Nanana no Maizoukin

Both main guys move into a apartment haunted by a girl. 

Similarities: Both involves girls who was murdered and was unable to rest in peace. Both involves boy who always gets pestered by the ghost of the dead girl. Dissimilarities: One has an extra horror genre, while the other one has an extra comedy genre.  

Both of these shows operate around "games" which throw the characters into life-or-death situations. Shiro/Sora and Tensai each show excellent analytical skills allowing them to create complex strategies to win the "games."  

A boy ends up living in a school dorm with a certain girl of great pivotal importance to the whole series, whether he likes it or not. Both takes place in a danger-laced city made up primarily of students being the majority population. Both protagonists unfortunately frequently find themselves risking their lives in dangerous situations by facing murderous adversaries, for the people they care about--despite claiming or wishing; to be just ordinary high school students.  

In both series the male MCs share room with a female ghost, and have to help them move on to heaven by solving their lingering regrets. Furthermore, both the series have a colourful supporting cast, and the overall tone is comedic and fun.  

Both anime feature the ghost of a girl who has died, but cannot move on to the afterlife. She haunts the male MC, with the hopes of solving her regrets. 

Both protagonists put their lives on the line, solving death-laden puzzles that would easily kill ordinary people. Both series also feature traps...in more ways than one, if you know what I mean.  

Okay, this is one weird recommandation, but I thought that there was a few ressemblance between those two show. Both of these show have a surreal feeling, but Hyouka always stay in the rational. The show introduce us to mystery that the main will have to solve. Nanana universe is way more excentric, but Chitanda from Hyouka sure is one crazy specimen! 

In both animes the school is "outside" the world 

The male MCs of these series are extremely similar in both their personalities and their personal growth over their outlooks on life. Subaru and Juugo each find themselves caught up in various and oftentimes dangerous adventures that are tied to the females and new friends they meet along their journeys. While the stories are different, the determination to reach their goals with optimism and a good natured attitude are the same in each series. The MCs are also a lot more serious than they let on and work hard to hide this from others. 

Both anime are related to a group of people who trying to solve the mystery of death of a girl. 

Mysteries requires deduction skills to create a solution against it. Rokka no Yuusha gives off a similar route: examining an environment of riddles to unravel the truth. Both MCs do their best in order to choose the best course of action when in dire situations. 

Both have similar settings where the trading, hunting or stealing of treasures is the main plot of the story Both protagonists have mysterious and strange back stories The female MCs are blonde lolis  

Main character transfers to another school and city. Finds an eccentric girl in his new home. There is a mystery behind her and he must uncover the truth. Similar theme and character personality. Both are comedy too.  

They've got the same silly adventurous vibe. They both have likeable (kinda cliche, but not in annoying way) characters and a good sense of humor, which is not solely based on fanservice. And cool action scenes, which you kinda don't initially expect in both of the series. 

Both of these shows were done by A-1 pictures, which means they both boast excellent animation, especially when it comes to landscapes and scenery. Both shows contain "rooms" in which the characters have to clear in order to proceed through challenges, often causing them to be in life-threatening situations. In both shows, plans are made by groups of people to clear specific rooms, making strategy a vital part of the series.  

Both have a main character trying to run away or branch off form there family traditions why ones Mafia family and the other some sort of underground organisation that steals artifacts, both seems similar with weird items with strange powers and main characters who pull through victory for his friends. 

Both protagonists are driven by major daddy issues. They both deal with weird people in weird situations at a fast pace. 

Both involves the MC who were from out of the frying pan and into the fire kind of situation, except the MC in one anime has a harem and a hot land lady, while the MC from another anime was surrounded by hummmmmm, a bunch semi average classmates and a bunch of weird old folks.