Aliens can build a spaceship that can travel millions of light years, can enter our atmosphere safely, yet they can't afford headlights or satnav?
I think I've stated before, I believe extra-solar life exists, it would be ignorant and arrogant of humans (traits we're good at) to think we are the only little specs of dust in the vast chasm of this universe. However, that doesn't mean I think little green men exist who have piloting skills of a drunk pilot exist.
We live in a universe of logic. It's just not logical for extra-solar or extra-terrestrial (though that seems almost improbable to come from within our own solar system) life to find us, to be able to enter out atmosphere (due to strengths of gravitational pulls, etc, think about NASA and re-entries) and last but not least, the contents of our atmosphere are almost certainly going to be highly poisonous to any foreign life. We wouldn't be able to survive in the several atmosphere make ups the Earth has had before this one.