Exactly. The current theory, I believe, is that humans didn't "exterminate" Neanderthals, we just out bred them. This might be due to differences in "character". I can't reproduce the argument here, and I don't have a link, so I'm being a bit vague but the point is, something in the Human mental make up caused us to form more successful communities than the Neanderthals. The several Hominins running around Europe in the past seem to have coexisted for some time, and interacted enough that some interbreeding took place. Over time, Neanderthal faded away, leaving only the bits of DNA we got from them.

There were never more than a few thousands Neanderthals. The rising tide from Africa just diluted them to 2%. They're not gone; they're here in you and me and Aunt Hilda.

We have 99% of chimpansee DNA and 60% of banana DNA. I don't understand how they measure the 2%, obviously it's a different metric.

EDIT: so apparently there is a way to distinguish DNA that originated in Neanderthals and we got it from them as opposed to DNA we both got froum common ancestors.