Not all of them are TV shows; some are movies. Many are made by J.J. Abrams, Tim Kring or their ilk. Lost is probably the Trope Codifier, though other shows of its ilk came before, including The X-Files, Babylon 5 and Abrams' own Alias. There are many, many, many more. These shows often either are Too Good to Last or, on the opposite end, instead, are Long Runners. Either way, the creator usually makes little effort to actually bother to ever resolve the show's central plot. See also Ontological Mystery. Examples