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.