WELCOME YOUKAI, HUMANS, DEMONS, MONSTERS, ALIENS OF ALL AGE AND GENDER. ENJOY MY PROFILE (or not)
Lists are all biased and none are based on objective critics.
Anime scores are:
In short, an anime with a terrible story can still have a score above 5 if the soundtrack and art are well done (i.e. Guilty Crown, Sword Art Online). The same goes vice versa, an anime with amazing story and characters can get a lower score than expected if the soundtrack and art are not done well (i.e. Ping Pong the Animation, a lot of the old classic series).
Don't like how I judge? Then don't bother looking at my list.
The art part is however, subject to change as art quality and standards gets higher overtime.
Oh and originality does not give bonus scores, nor cliches lowers a score. Execution and result matters more than that. Why you ask? Simple, originality can be very misleading and is horribly subjective. To some it could be innovation and an original idea, to others it is nothing more than a random failure of a storytelling theme. Popular example is Shingeki no Kyojin or Madoka Magica. All of these however, can be applied to general themes. For example comedy, one can find Nichijou completely boring while others could laugh like there's no tomorrow at its jokes.
If you were to pay attention, the completed list doesn't have many series scoring below 6. There is a simple reason to it, why complete a series you deemed terrible? For the purpose of being a completionist? Wanting to know what happens next despite not liking the series? I find such actions.... pointless.... unless you like to torture yourself in which case I won't judge (After all, torturing oneself isn't as bad as it sounds like.... heh...).
Adaptations are scored differently and should not affect the main scoring system (Example: Tokyo Ghoul) however it can be noted if a series do have a terrible adaptation of its source material.
Manga is 50% story 50% art although this scoring system will be different one day.
Novel is very biased and scored based on nothing more than level enjoyment. This is especially due to the easiness of mis-translation between Japanese and English on Novels more than Manga or Anime.
It's quite a wall of text (or not) but if you can read all of those and not simply click away, then I won't mind being your friend (or not).
P.S. All scores are biased in one way or another, unless I made a review for them.