I forgot to add this in regards to storylines...
Essentially, there are only so many words in the English language, and only a few of them are intriguing in a certain order and sequence.
In other words, every single story or plot you see now, has most likely existed prior to your thinking or hearing of it. The Doom story (scientists uncover new technology -- bad stuff happens -- people die -- lone hero saves the day) is a story archetype. There are many archetypes in writing, and unfortunately they're so prevalent today that sometimes people don't even notice.
Really, the only thing a writer can do is change what happens in between the beginning and end and at least try to make it seem
By the way, my reasoning isn't unique... it's been stated before.
There are not many original thoughts.