Writing
Water
The s/l and lately to see if the writing gets better and to see who gets fired next and (fingers crossed) maybe it will be JFP.
Without the writing there is nothing
The story lines, the actors, that make you keep watching every day..
While I don't watch them, two of the basics are character development and audience involvement.
I would say the substance is glycerine and or lye
Is it the acting, the story telling, or we just like an escape? I have to admit sometimes I just watch because of an actor or two I particularly like. They have to do something good with such poor material sometimes, it amazes me how they do it. Lots of them are underrated.