A, B, and C
Especially if you want fame for the piece you're writing.

C-B-A
D is not relevant ^^

why would someone vote for fame? ;A; lmao

I can't decide for one of them ;A;
Grammar and vocabulary is very, very important since there are also a lot of english native speakers on AFF. I can't read a story which only consists of direct speech or aren't descriptive enough, where I have to correct every sentence in my head. It just hurts my eyes Q_Q Of course we're all not flawless and non native speakers make mistakes, but then again - why not asking for a beta reader?
Description, characters, emotions - YES! I love fanfics which is very descriptive and don't have A LOT of direct speech, but where the feelings and the environment and everything else is described. The characters are very very important for a story, because without characters no story, so they should be pretty unique and their feelings and motives understandable.
I think I speak for most of the readers if I say that we don't like cliche storylines xD I'm sick of seeing them.
Fame.. A little, to be honest. When a story has 20 chapters and 'only' 10 subscribers I'd automatically think: Okay this story is not so good. Unfortunately, it always turns out to be so :(
Yeah, hehe, just my 2 cents xD

Ah, I'm torn. Hehe. I mean, I couldn't force myself to read a story with an interesting plot if I had to mentally edit every sentence. And those with few grammar mistakes could be boring as well. I may not have problem understanding the story but if it bogs me down, I don't think I could read it. Then you get something that is reader-friendly, with an interesting storyline and then you can't relate to the characters. My standards seem so high when my stories aren't that good either, lol.

Frankly, as long as the grammar is not too horrible and the characters aren't too bipolar or feelingless (and I have been charged guilty for doing that once... It's hard to make your characters really alive), I think that the plot is THE most important part of the story.

I'm a mixture of B and C because I think an original idea makes a story unique and interesting to read while choosing food characters to carry out emotions is really important too ^^ this is just my opinion, author ~ nim hwaiting! ≧﹏≦