all three of Kyoto Animation's adapations of Key's visual novel games and this is the order I like them.
And here are my favorite girls from these shows.
Air: Meh lol
I wasn't really into Air. It isn't bad, but the story is a bit strange. Kanon starts out normally enough, but there are a lot of surprises and strange things occurring. Then Clannad, along with Clannad After Story, is awesome and has a number of likable characters. It has funny parts and a couple parts (mainly in After Story) where it gets really emotional. I personally did not cry, but I did well up a bit (I think anyone would).
So yeah, check them out if you'd like. They're all love stories with comedy and emotional parts.
(Not very in-depth, I know. I'm not reviewing them. I mostly just wanted to say I like Tomoyo, but added more ^^ )