Re: What makes a good anime.
I really can't believe that Attack on Titan is being mentioned as 'nearly' perfect when it's still ongoing. Can't you guys wait till it's over to rank it? What if the series limps a bit as there's more episodes? Judge it in its entirety. Yes, it started off on rocking heels but what matters is the finish line.
As for the thread question:
Well, taking good things up - there are series that decide to choose an original concept (like a power, a curse, a situation) and develop the concept. Thereby, they'll expand it by showing its origins, its aftermaths, its impact, the complexities of it and the influence it got on the plot. Then we got some series, that are qualified as excellent as they got no plotholes in their story and its stories flow smoothly with humor, tragedy, drama, thrills, realism ect... and with a right tone to its genre. And then, we got series which got awesome characters that are continuously showing their facets and also being developed.
In a way, an perfect anime would be one that got all these 3 elements; provided that it avoids some drawbacks and got some necessary advantages. Like the lesser the cliches characters/concept, the better! The right dose of fanservice - neither excessive nor overbearing and also not used in wrong moments. Then we got correct character interactions that appeals to the viewer. The length of series is also a factor - should not be stretched up to a point where it limps the series but it should also not be too short that it leaves minimal impact. Also, it should cater to its genre audience. Like if it's a shounen, it needs to have great fights, if it's a thriller - lots of adrenaline thrills, horror - more gore and scares and so on... And lastly, needless to say, for an anime to be perfect - it should possess great design, great animation, great seiyuus and great music.