There are many reasons why one can like/dislike a certain anime/manga.

As for an anime,

Music (Opening, ending, OST, etc.)
Seiyuu
Character
Graphics
Plot
Scale (?)
Theme (Maybe type of anime?)
Dyanamicness

As for a manga

Plot
Charater
Mangaka
Cover
Scale (?)
Theme (same as above)
Toning

That's all I can think of now. Of course, you're welcome to add other things you think are important to an anime / a manga. Tell me manga/anime then what you think is most important about it.

And as for me, for anime I am concerned about the music lately. For example, I watched Kannazuki no Miko because I heard both OP/ED were sung by KOTOKO.

And for manga I think I tend to think more about plot. Whether it be action, comedy or love.

P.S. Scale's there because I love large-scale stuff. Mamoru Nagano's Five Star Stories hooked me with its huge scale setting.

P.P.S. I don't mean to say that other traits aren't important. It's just so happens to be that the current I thinks some traits are more important than others

P.P.P.S. Just to get it clear, "theme" defines the "type" of anime/manga. It can be drama/action/comedy/fantasy whatsoever.

Good list of stuff.

Anime:
Unique characters
Voice Actors
Music
Plot
Visuals/Graphics

Ma(...)

plot
characters (development)
graphics/animation
music
voice actors

Anime-

1.Character
2.Music (Opening, ending, OST, etc.)
3.Animation
4.Seiyuu
5.Plot

As for a manga
Character
Cover

just everything!

Anime:
Animation
Plot
Characters

Mang(...)
Character Designs
Plot

i go for plot and story

from anime i think that noyt only that aspects but it needs something like magic and its diferent from person to person one example is like FLCL its... awesome

1. Genre
2. Art
3 Character Design
4. Plot
5. Emotional pull/Comedic value
6. Combat

For manga :

1. plot (what it talks about and how it's been told);
2. art design (if i like it but i don't stop just because of that if the story is good or the characters great i'll read it);
3. characters (what make them attractive).

For anime :

4. music (op principaly);
5. seiyuu;
6. the dynamism of the animation.

Anime

1.plot
2.art
3.charicters
4.act(...) (makes the action bett and the serese dosent get soggy)
6.vioce acting

Manga

1.art
2.good toning
3.plot
4.page design not too confuzzling or too simplated
5.dynamic pictures just make you say WOW.

Anime

1. Story/Plot
2. Characters
3. Acting
4. Art/Graphics
5. Theme

Manga

1. Art (The art is what first draws me to read any manga.)
2. Story/Plot
3. Characters
4. Manga-ka
5. Theme

To me characters are the biggest reason for me to like an anime followed by story. However having more good points is a good thing as well.

Thanks for your replies. Added some more fields based on them, and also added a line to get the "theme" part clear.

I like it for its dramas and plots but also because it makes me laugh alot

Quote: i go for plot and story

dito rin

Usually, if I really really really like an anime, it's because I've fallen for one of the characters. However, I can find myself liking a character but not the story so much...

Good art counts for a lot, but most of all, I think, is the plot. I love manga that are full of twisted, angsty romances, a dose of bloody violence, plenty of bishounen, but mostly one that makes you think. The kind of story where you become wrapped up in it like you're there... I like that for books, too. I think CLAMP is good at that; that's why I like X and Tsubasa so much. Not only is the art good and the characters compelling, but the stories are just awesome.

as long as i like the animation/drawing style and it keeps me interested. I hate anime that's just a different version of what already exists.

- music
- action/fights
- story
- humor
- some seriousness
- voice that suits the character
(I saw an anime with a girl that had an extremely odd voice... 0_o)

For anime:

- story
- characters (desigh + personality)
- actions/fights (animation)
- scenery setting (art)
- background music
- opening+closing themes

humour is not really important for anime, i don't really care. but humour is VERY important for MANGA, otherwise i'll fall right asleep. i can watch serious stuff, but i can't READ them.

1. Character designs / Art
2. Story

just 2 for me. yeah. Art is no1 for me. even though the story sucks i still watch it beacause its good to look at.

The most important in an anime (and a manga) and the only is the drawing.
I could see a very bad anime if the drawing are as I like it.
But it's difficult for me to see a very good anime if I hate the drawing !

For animes:

At first, what draws me in is the art/animation.
After watching an episode or two, what would make me keep watching is the story and music, if they are interesting and fun.
However, one thing that would probably be more important than the story is the characters. I often watch animes just for the characters.

1-the most important is the drawing.
2.story
3.idea of the manga or anime this is also very important to me
(if the drawing is not very good but the idea of the story is
very interesting i will go for it)
4.character