Pop culture’s graveyard is littered with the corpses of many fine television shows that were cancelled too soon, shows that couldn’t find an audience quickly enough to hold off twitchy executives who lacked patience and vision. Occasionally, there are series that manage to survive if not quite thrive in terms of bigtime ratings. Two from the 1990s that come to mind are Homicide: Life on the Street, a stone-cold classic cop drama that was universally praised but criminally…