Most Helpful Guy
The only proper response to this is "I don't know." There are so many potential factors in the forming of life that it's impossible to say. We haven't seen any evidence of them yet, contrary to what you see on the "History" channel. And everyone says it's really likely, but that's only true if you assume that life has a good chance of forming on any planet with liquid water and an atmosphere, which is a blind guess. The odds could be one in a trillion-trillion-trillion, in which case we might be alone.
Most Helpful Girl
The galaxy is too huge for aliens not to exist.