Of course the concept! Is it bad, the image can still be so well done, it will never impress me. Just a beautiful picture, of which there are already too many!!

Quality, since the clever mind knows that could account for a bunch of the others - Originality is a plus too and so are beautiful colours, but I think the subject of the work, what it's a picture of still matters most to me, of course - I wouldn't fave a drawing of a thing or character I like if it's crappy

My first gut reaction to a picture really determines how I'll evaluate it logically. All of things you list are important but I think they work best in pairs. I mean, the quality might suck but that's something that can always be worked on. I chose "concept" simply because that's ultimately the basis of almost all artwork. It's something you can't change while all the other things are fixable in the end.

Everything you've listed has importance. But I voted for "Composition" because in my view it's the single most important aspect of any image (and often the most difficult to define!)

It's kind of unexplainable, but it's obvious what pics I like and dislike.