Yuu☆Yuu☆Hakusho: Meikai Shitou-hen - Honoo no Kizuna

Both films have similar endings, as they use friendship as the main element to solve the main problem, typical of animes Shounen. and the characters Hinageshi and Kotoha are similar because you fulfill the same function is their respective films. 

Both series deal with demons & supernatural enemies. Mikami offers more comedy while Hakusho provides more action.  

Both series are Shonen Jump titles dealing with demons & the supernatural. Both features serve as good introductions for their respective anime series. The Hakusho film has a more traditional story of defeating the movie villain & his minions, while the Hell Teacher Nube OVA is episodic with its final episode being awesome with its demon battle centered story.