Super 8 has a coherent reveal of the mystery box. Lost did not and disappointed at the end.
The kelvin timeline from when he rebooted Star Trek is sort of mystery box but then we learn who Nero is in a coherent way early on as well. I did not like that JJ destroyed Vulcan and frankly made a confusing alternate, darker timeline at all. The reboots are good movies but they were not good Star Trek movies. Missed opportunities to explore the Roddenberry style themes of humanity and deep moral questions under a backdrop of optimism.