I do believe there is alien life out there. It is highly probable. There are billions of planets, and although we have found very few which is in a habitable zone, and contains water - we have to aknowledge that we haven't even discovered one percent of all the planets or other habitable objects out there. In other words, the probability of something like the earth to happen is minimal. However, the quantity makes up for the isolated probability.

The question is, however, is there intelligent life out there? While I do believe that there are relatively complex organisms habitating more than one place in the observable universe, I'm more skeptical to what are typically perceived as aliens. The ability to i.e. fly without earodynamics can be explained with electromagnetism, or practically applied quantum physics. We are however, not able to explain how those alternatives (incl. more) could work practically with the knowledge we possess. At least we aren't to my knowledge. Therefore I choose to doubt green men going around our atmosphere at mach 248 until further. Green grasshopper-elephant-armadillo-like creatures on a very distant planet however, maybe...