Famed British astrophysicist Stephen Hawking says that aliens likely exist, and, unlike Eliott's bike riding buddy ET, may not be friendly.
On the other hand, Don Henley says They're Not Here, They're Not Coming¹.
As you know, I'm a huge fan of Henley's, but from a scientific standpoint, I might have to give the edge to Dr. Hawking. Maybe Henley's not really denying the existence of the little green dudes, but just saying that if they're really outfitted with higher intelligence, they could find a much more hospitable host planet.
¹ From the CD, Inside Job, 2000