Sometimes a really great story just doesn't get a chance to conclude on TV, and there's nothing anyone can do about it but wonder what might have happened. For me it's Stargate Atlantis. The showrunners had plotted out a final season, and when that didn't happen they wrote a movie which was cancelled also. Years later I still sometimes hope they'll announce some sort of final movie or miniseries but I know the ship has probably sailed at this point. What other shows do people still want closure for?