I have been REALLY impressed with the submissions we've been receiving at Electric Spec . The quality and the quantity has been amazing. (More on that later from Dave.) Thank you, Authors!
What this means, however, is we are looking for stories that have something special. The 'three legs of the stool', as Betsy would say, have to be solid and there has to be something more. In my opinion, originality can really differentiate a story. Do you have an idea no one else does? If not, get one. :)
I also think an excellent story needs to deal with more than one idea, both an internal and an external arc at a minimum. I'll give you an example. Last night I reread Oceanic by Greg Egan. Wow. This piece deals with several ideas including family dynamics, gender exchange (!), religion and its origins and genetic engineering all set on a unique world. I'll say it again: Wow.
My last opinion of the day is writers need to read and think about what they read.