To be honest, some of them are good. Some are "less than good". I've heard one really neat, original idea that I think should be developed.
But the question that I ask in response to my correspondents is about the key idea behind their show: in the simplest terms "Why Should I Care?"
Why should I care? Why would I (or anyone) watch your show instead of some old House re-run? What's in it for me, in terms of the investment of my time and attention?
When you have a good answer to that question, you're well on the way to developing a successful pitch. So what is the answer?
Strong characters. Strong motivation. Clear goals. Clear obstacles to be over come.
All that 'writer' stuff.