Is it possible to delete a quest (before you finish it, that is)? Or will it show for the entire game?

I don't believe so...I've got several pending that I can't ever complete, and they don't disappear from the list, nor can they be hidden.

Come on Bethesda, is this so hard to add in with the next patch? (Group all the Quests "passed" and "failed to complete". That way it's way easier to tell which ones we CAN complete vs. the ones we can never complete).

Sorry to hear that,joe, but maybe Bethesda will listen to your suggestion.