We're not even the only intelligent species on earth -- just the most intelligent extant species -- and it's possible that at least one other species may have been smarter than we are.
The likelihood of intelligent life on other planets seems much greater than the likelihood of god. However, it would still be absurd if one were to convince oneself that one is in possession of infallible alien writings or if one were to have meetings to communicate with the aliens, build temples for them, ordain priests for them, obey prophets who claim to speak on their behalf, or otherwise delude oneself on the subject.