For those of you who have e-queried me (using my website submission form) and gotten a pass, you know that my standard response is that your project "... isn't right for me."
I chose this language carefully. Your project might not be right for me because I think there isn't sufficient publishing viability, or it might not be right for me because it's in a genre I'm not interested in representing right now. It might not be right for me because I think your writing could be improved, or it might not be right for me because you can write but the story lacks originality.
The common thread to all of these possibilities and any others is that I've passed on reviewing your work based on my own subjective criteria. So please remember to take my response with a grain of salt and continue to query. But please don't ask for for more details about why I'm passing or a list of other agents to try.