Total Recommendations: 2
Both Aria the Origination and Haibane Renmei are slice of life, with themes of growing up and a strong melancholy undertone. Both also have beautiful art and settings inspired by Europe, though Aria's is Italian and Haibane Renmei's is Central European. Haibane Renmei is not as sweet and happy as Aria, and it uses fantasy elements where Aria uses sci-fi elements, but both shows are beautiful, moving, and combine slice of life stories with great art and likable characters.
Both shows have a similar feeling--lightly harem, lots of otaku-oriented references, mostly about character and relationships, not too much high-concept and nothing supernatural. The theme of acceptance is very strongly presented in both shows. Both are primarily comedy with some dramatic moments. Both have sequels that differ in quality from the original (except that Haganai's sequel gets better, and Ore Imo's gets worse).