Not so much the "gods" living on Earth, but the interaction of the "gods" with humans.
Seems to be a recurrent theme. UFO's does not necessarily mean extra-terrestrial though. Could be an advanced race that lived on Earth, but didn't conquer others, nor spread their technology and ideology. Kind of like Star Trek and the Prime Directive.
Or, let's go with Icke and have the ET's from another dimension, not another physical world.
Still, some interesting theories, and less far fetched than some competing ones. Or no more far fetched ..