It's actually harder to think of something generic enough it could spawn 2000+ games and be original.

I like the idea of machines / vehicles / creatures running amok - could be interpreted a number of ways, from a runaway train, to herding animals etc.

That or I reckon something with sticky / magnetic abilities could be cool and interpreted a number of different ways.

Like some sort of physics sim with electromagnets, or cats climbing on curtains , lizards up walls, or spiders down drainpipes , or the whole world covered in treacle.