It's dangerous to extrapolate on the basis of a single sample. It is likely, given thermodynamics, that life exists elsewhere. It seems plausible that the vast majority of life "out there" is analogous to our bacteria. We have no idea how eukaryotic life began, but it seems to have been an extremely unlikely once-only event. So complex life may be very rare. Next up, we come to the question of intelligence: in the 4 billion years life seems to have existed on Earth, tool-making life has evolved only very recently and there's no reason why it should ever evolve elsewhere. Fish have been around for at least half a billion years; none have much in the way of intelligence. Dinosaurs were highly successful, and none developed what we'd consider to be intelligence. Where we do see intelligence, most is aquatic which means no tool-making (try smelting ore underwater....). Even if we get to the one-in-ten-billion chance of tool-making intelligent life, the vastness of spacetime means the probability of two such civilizations overlapping so as to permit interaction of any kind is essentially zero. Therefore, to all intents and purposes, we are and always will be alone - until we accidentally exterminate ourselves through our congenital folly.