Makai Senki Disgaea

Very similar art style and humor. The demon lord or in this case vampire lord meets a unique person. He helps her out and on the way becomes more human like than demon/vampire.  

Both series take place in a demon realm that parallels the real world, where the main characters are young humanoid demons seeking power like their past relatives. Both have strong comedy and fantasy elements. 

Although the story itself is not so similar with each other, but if you loved the prinnies in Disgaea, you'll love the penguins in Mawaru Penguindrum 

Both has a non-human guy as the lead character followed by other non-humans. Both also has a kawaii weird-ish kind of girl in it. Flonne for Makai Senki Disgaea and Mayura for Matantei Loki Ragnarok. Also, both male main characters soon being to like the weird/somewhat annoying girl. If you don't like it no-biggie, it's just a recommendation! +_= 

Both shows have a lot in common. If you just go based on the plot synopsis the two shows seem very different, but I defy you to sit thru an episode of each show and not see the similarites. Same voice actors (at least for the english dub), same animation style, same dark, quirky type humor. Basically if you like one show you'll almost certainly like the other. 

Both of these animé involve an incredibly-powerful, cocky, hot-blooded protagonist who had a demon father and a human mother. They also posses large, easily-concealed swords with which they use to slay countless evil demons. They lead a group traveling on a journey for the restoration of power and battle several mighty adversaries, some of which just keep coming back for more! Both of these half-human, half-demon protagonists also have to deal with a girl from someplace else, who can wield a magical bow, and is very insistent on shaping up the protagonist and softening him into a better, more mature person. 

Both feature abrasive mcs who have to work with others to achieve their goals as well as being based on a notable jrpg franchises as well too. 

They both have this strange kind of humor, but in Disgaea it's a bit darker, because it takes place in the Netherworld. Both animes have this 'love' issue, in Mon colle Knights it's jealousy, in Disgaea they don't seem to understand it. If you plan on watching Makai Senki Disgaea, know that the episodes are much easier to find then with Rokumon Tengai Mon Colle Knights. 

Both have tiny lil and pretty main characters who travel and have many adventures with fun or danger in a fantasy world. Both are based on RPG videogames too. 

It has the same kind of humor in it I find. Despite being so diffrent. 

In anime are Angels and Demons. Chrno is similar to Laharl (child form) and Vyers (adult form) from Makai Senki Disgaea. 

These two anime are totally different in story and number of episodes. But if you're like me, (That is, you enjoy comedies with light action scenes and you're also a fan of insanely strong heroes with blue hair) then you should check out both of these shows. 

Similar themes and archtypes but different settings. Both main characters are demon princes with scantily glad sidekicks. Enma-kun is a dirty minded Earth based cousin of Disgaea with more references. I think if you like one you'll like the other