When you say "the only thing that UFO lacked was an ongoing storyline", do you mean the original X-COM/UFO, or this project (UFO:AI)? There kinda/sorta is an ongoing storyline, or at least background - true, it's in the ufopedia, but if you go to the very top section (am in combat right now, can't remember what it's called, "background" or something similar), it does fairly well describe their "future history", from the present 'till the game's "present day"...afaic, anyways.