Yes, I believe that we are not alone in the Universe. I also must point out that I'm an atheist, so I don't believe in God - there is no religion that could cloud my views on that matter. I'm not afraid that contact with intelligent alien races may destroy the foundation of my faith... cause it doesn't exist.
I believe in science, and math says that 'yes, there is the possibility that we aren't alone'. Though I think the reason why we haven't found any evidence yet is that we aren't technologically advanced enough to find it (but that doesn't mean we won't find it in the future). Of course it doesn't mean that this extraterrestrial life is as advanced as we are, but there could be a planet flourishing with microscopic life, or a planet with creatures resembling Earth's long extinct dinosaurs. It would be really arrogant of us to think that we are the one and only life form existing in the incomprehensibly vast Universe with billions of planets and stars.
In the end however I really enjoy the idea of technologically advanced alien species observing us from the safe distance and waiting for the right moment to get in contact. Imagine the possibilities!
I'm sure the universe is full of intelligent life. It's just been too intelligent to come here.
― Arthur C. Clarke