D.C.II S.S.: Da Capo II Second Season

They both have: 1.) Wonderful artwork- 2.)A slight similarity- 3.) good romance- 4.) a very dramatic scene like this clannad- 5.) Otome looks so youthful, beautiful, and cute like Nagisa!!!- it gets very dramatic at the last few episodes. 

Someone loses someone that they love and involves an dues ex machina ending as well. 

Yo. the relationship between the protagonist is the same [ultra spoiler theree] :< but it's too hard to explain w/o spoiling >w< anwaiz, AKANE is more harem/ecchi, whilst DA CAPO II SS is more romance/mystery-ish 

Yooooo~ similar relationship, again! onnnii-chan? otokou-kun? explaining more would give spoilers :< both aren't ecchi/harem much and have a decent amount of romance in it :33 and to those who watched Canvas, DA CAPO II SECOND SEASON is more SADDER at the end :P 

They're both harems with a touch of supernatural and the main characters are just lovable assholes. The greatest similarity between them are the opening scenes, where "a certain character" talks about their dreams. If you liked Da Capo II Second Season, I would totally recommend Kanon 2006 since it is basically better in every way. (Ex: character development, animation style, story telling, etc) 

the art is similar and Yui Horie is in it but this is more deep and not as funny but their is humor 

instead of sakura tree, rainbow was used. the female protagonist looks like kotori