I won't rank them, because they're all great, and I wouldn't be able to decide which goes where. So, in no particular order:
* Clannad + After Story
A series with a lot of heart. A deep boy meets girl story, with great plot development, good comedy, and real emotional impact. I have never once shed a tear while watching an anime, except this.
* The Pet Girl of Sakurasou
The most masterful use of a love triangle I have ever seen. Every character has strong defining features. This show wins the "makes you care about the characters" award hands down.
* Listen to Me Girls, I Am Your Father
The main character is a hero, and Hina (the youngest girl) is kawaii + cute to the 500th power. Anybody who has suffered any family issues will fall in love with the main characters and cheer them on every step of the way.