How's this intro?

Long ago, aliens invaded the Earth. They had such powerful technology that we were no match for them.

So, we built powerful robots to fight them. That worked for a while, until the robots became self-aware and decided that humanity was the problem.

And so, we created genetically-enhanced superheros to save us from the aliens and robots. But in time even they decided we just weren't worth saving.

Life isn't so bad. You stay down, keep quiet, don't give them a reason to call pest-control, and you should be fine.