Been a while since I've read it, but I recall the humans 'won' Footfall with a combination of "clever monkey" subterfuge and the discredited Orion atomic rocket concept. Not scientifically discredited, mind you... but they launch from Earth's surface (Seattle, if memory serves) with the excuse - for the resultant radiation poisoning - that the city's destroyed anyway.

In other words, it would be easy for an aggressive ETI to take Earth from us and the fact that none seem to have done so means that such conquering beings either do not exist or they just haven't found us yet (it is a big galaxy, after all).

The first, and in many ways still the best example: Wells' Martians. In Those aggressive ETs had taken Earth from us; they neglected to also take it from the true rulers of the planet, the bacteria (see also selected works of Stephen Jay Gould). But what can you expect from a "dying civilization" straight out of Percival Lowell, so low-tech themselves that their spacecraft are ballistic projectiles shot from a cannon?

Of course one hopes that a society that can traverse the stars would be peaceful, but then again we do have the example of the Borg (they mean well - they think everyone should be as enlightened as them).

ET himself; the aliens from Close Encounters; Vulcans, Bajorans; whoever made the monoliths from 2001... the list of benevolent aliens is pretty short. Ever wonder why?

Of course, they are fictional, too

Yup.

Which leads to another point - with a galaxy of 400 billion stars and probably even more planets, comets, planetoids and countless resources, why bother with Earth and the talking monkeys with car keys? Other than how NOT to behave, what could they learn or want from us?

That we're here, for one. Of course, that assumes they'd share our insatiable curiosity about everything, including how monkeys got car keys and learned to talk.