Anime Easily the best among the three Key Ani works.
Clannad combines Slice Of Life, Romance, Angst, Family, Comedy, and Fantasy in one cohesive setting. A Genre Buster if I've ever seen one.
Beware of SPOILERS!!!
Plot: 10/10
The idea of Tomoya helping Nagisa gain confidence by helping her reestablishing the Drama Club was a foreshadowing of Tomoya's Jerk With A Heart Of Gold nature, as he really acts like a Jerkass sometimes, especially towards Sunohara. He does inadvertently gather his harem in this manner, but he really shows how sincere he is in helping them.
The second season was great in showing how Tomoya matured from the lazy delinquent he was in high school into the hard-working person he was since that point. The Character Development was really realistic, as since he had a steady girlfriend, he decided to get his act straight in life.
The buildup towards Nagisa's death was brilliantly done, a Player Punch if I've ever seen one. Crying is the only option.
When Nagisa died, Tomoya showed a very human reaction: regret. His in-laws were all supportive of him during those trying times, so they'd be an example of the ideal in-laws. Tear Jerker moments abound here, and none of them were uncalled for.
Lastly, the ending fully encompasses the fantasy element of the series. While many people view it as a Deus Ex Machina Reset Button Ending, the game has this as the "True Ending," so it was justified.
Art: 10/10
Kyo Ani worked on it. Need I say more?
Themes: 9/10
The OP for both seasons and the second season ED was of superb quality. However, Dango Daikazoku felt a bit out of place IMO, although aside from being Nagisa's favorite, Rule Of Cute applies.
Overall: 10/10
Clannad is a story about life. Many valuable lessons in life can be gained from this series, as most of the dilemmas are realistic enough for most viewers to relate to. Tomoya and Nagisa's love for each other is an ideal romantic relationship. The Drama Club is a true Nakama; they've always got each other's back, no matter how difficult the situation may be. The animation is of superb quality, and the pacing was just right. One of the best series ever.
Anime The Crying Game
It bears mentioning that Kanon is but a mere dress rehearsal when compared to what Clannad attempts, which is to not so much tug at your heartstrings as practise virtuoso nineteenth century harp concertos on them. Laughed when Bambi's mother died? Think Grave Of The Fireflies would be much improved with the addition of a riff track? Clannad invites you to bring it on.
It would be redundant to summarise the plot: partly because the previous reviewer has already done so admirably, but also because it's not wildly divergent from others in the genre (especially with regard to its elder siblings). Boy meets girl; everybody cries. In a welcome departure from the norm, though, the canon relationship is allowed to develop organically throughout both seasons, and its presence is still strong in arcs ostensibly focussed on other characters.
The militant 'leave not a dry eye in the house' approach favoured by the writers may legitimately be found manipulative: the last act of ~After Story~ is emotional extortion of the most baldfaced variety, and one starts to wonder how much more of a trauma magnet they can make out of Tomoya. It's not that all the major narrative devices are designed to push viewers' buttons, it's that they're employed with somewhat predictable alacrity. By ~After Story~, you're practically counting down the number of episodes before it's time to reach for those tissues; towards the end, you're counting in minutes.
I make it sound like this is a bad thing; quite the opposite, really. After all, drama serves to exercise the audience's emotions. Even if the resolution of the central tragedy invokes the supernatural with an easy convenience, it's not as if you can say it was undeserved. In keeping the True End mechanic of the visual novel intact, the spirit of the game's ending is faithfully preserved: they say it's darkest just before dawn, and it's nice to have the ensuing cartharsis. Which is a fancy way of describing how relieved I was that it didn't end on what could have been one of anime's bleakest notes.
So, who else fears the worst for the inevitable Little Busters adaptation?
Anime Watch The First, Consider The Second
I feel that I need to make a distinction here. Clannad and Clannad ~After Story~ are two different shows who just happen to share a setting and characters. The former is a high school slice-of-life romance/harem anime which was well written and executed. The latter, a darker, more cynical continuation which explores issues of family, responsibility and, of all things, death. Which, coincidentally, was written even better.
I'll start with the things that both share. I watched the dub, and the voice acting was pretty good, by my standards at least. The voices suited the characters well and remained consistent throughout both seasons. The animation and art style in general were also pretty decent, nothing stood out as bad and quite a few moments that I would hesitantly call 'great'. The scenes in (for lack of a better term) 'the other world' especially, were done really well.
But here come the differences. The first series is a light-hearted comedy/romance anime with harem aspects (although it's pretty damn clear who is going to 'win' that) with a lot of nice, heart warming moments. The second series tends more towards the Tear Jerkers. Admittedly the heart warming moments are all the more so because of shed tears, but still... After the first few episodes, the comedy aspect is gone and the romance follows suit soon after. Then it gets darker and I wouldn't be entirely wrong to call it a tragedy from that point onwards.
The OVA's, made specifically to please the shipping fans (a group to which I belong, much to my shame), deserve a special mention. Their stories are separate from the actual plot and are essentially the 'what if' scenarios for the other members of the harem from the first season. I can't quite put my finger on why (probably because I can pretend that my ship wasn't sunk, but hell will freeze over before I admit that), but they gave me a nice sense of… closure.
For a recommendation: I would suggest that if the romance/harem aspect appeals to you, then you should definitely watch the first series. As the second falls under a... different heading, I would suggest that only those who loved the plot of the first and want to see it through to its conclusion stick with it. As for those who enjoy that warm, fuzzy feeling: approach with caution, but still watch it.