I need a sad anime on par with Clannad and Angel Beats.
Chuunibyou is about a 'geeky' girl... Western equivalent might be goth? It's mostly comedy
Hm. Maybe look into Honey & Clover? It's got ups and downs, I enjoyed its tone.
(I don't have and H&C hentai, so tits)
Boku No Piko is what you're looking for
I like that it's mature.
The characters are university students, not grade schoolers.
You can always try one episode if you're interested.
Toradora straight up. Made me rethink a bunch of things..
Now and then, Here and there. Will tear your fucking heart out, seriously if you want sad this is it. Its a bit old but my god man.
Wolf Children. Its a movie, rather recent, strong story and highly recommended.
Cant think of anything else off the top of my head.
Ah shame to hear it, as someone who got raised without a dad it just struck a strong cord all the way through.
I havent seen Kanon so i cant help with a comparison.
Toradora is a romantic comedy but it has this real romeo and juliet kinda vibe which once your good and suck into the show, really gets you in the end.
Now & Then, Here & There
Prepare to get emotionally pounded by this anime. It will throw you gut punches left and right then by the time you get to the end you'll be emotionally exhausted for like a day or so.
Just make sure that if you watch it, watch it with the english dub. It simply won't be the same without some of the voice acting done for some of the characters in english, most notably the main villain.
You can watch it for free on Youtube.