Quote from a guy on AnimeNewsNetwork after Clannad After Story reached #1 (currently #2 best rated on ANN)
Now I have a problem with this! First off, Clannad ~AS~ is still the best rated TV series, so congrats for the viewers getting that right. However... 'The Disappearance of Haruhi Suzumiya' as #1? I'll be the first to admit I think it is a really well done movie... assuming the audience knows the characters and general storyline. 'Disappearance' is not a stand alone piece/movie. It would be like watching 'Star Wars: The Empire Strikes Back' without watching the first movie. Sure, one can follow along with the story, but that doesn't mean it makes a whole heck of a lot of sense. I'd even go so far as to say 'Disappearance' poses a greater issue because it entails flashbacks and timelines the audience isn't aware of unless the prior seasons are watched / light novels read.
One could suggest that ~After Story~, as a sequel series, has the same problems; I respectfully disagree. You see, I watched Clannad ~AS~ before Clannad. My friend happened to have the several series available for me to watch, so I chose a show seemingly at random (I saw all the shows listed but I had no idea what any of them were). ~AS~ was off to the side from the other shows, so I decided to watch that one; sufficient to say I was happy I did. Why is this important? Well, watching ~AS~ is what got me hooked on 'non-mainstream' anime. (examples of 'mainstream' shows include any heavily promoted anime in the western world, such as Sailor Moon, DBZ, Pokemon, Yu-Gi-Oh, etc.) The storyline was so powerfully delivered that without any prior knowledge of the series to that point (S1), I was able to learn the background of the characters to a significant extent and understand their struggles without any outside assistance (while changing my life in the process). This is something that 'Disappearance' and many other shows lack; once again this is not to say 'Disappearance' wasn't a great movie with the proper background knowledge (it was). Rather, as a 20+ episode self-contained season having to keep up high levels of enjoyment throughout every episode, Clannad ~AS~ deserves additional consideration than what I am guessing it received from the ANN community.
I could go on further, but unless I go into a breakdown of the positives and negatives of each story, this is as good a point as any.
Long live ~AS~. Long live CLANNAD. Long live KEY.