I enjoy a mystery. Not the who killed Miss Plum in the library with the hatchet kind, but stories that keep us wondering.
Why is this happening? Who started this trail of events? That unknown element keeps me watching -- often intently.
We don't have a lot of time to tell our stories in the few minutes that comprise our pixelated tales, but we can still follow the intent of some highly regarded films. "Momento" and "Sliding Doors" come to mind.
In the machinima world, the best example I can think of if Hypatia Picken's Cloud.
For me, there is something about having secrets revealed slowly that leads to the enjoyment.
Perhaps a thought for your next film.
It is for mine.