I share the opinion that we aren't the only living things in the universe. Just imagine how big it is and which little piece of it we really know. I mean, we don't even know every kind of life on our own planet. It'd be presumptuous to think we are the big exception. Maybe that's true for this galaxy but there are so much more. A few hundred years ago we didn't even know that the earth is round and now that's even for the catholic church official. So we can't know what we'll know in another few centuries. Another point is the definition of life. For us life needs water and an atmosphere like ours to exist. But what if anywhere a way was found to live on sulfur? - remember: we live on oxygen, plants don't any we haven't even left our house to find such different creatures. I'm not sure if anything with arms and legs and a brain like we know it exists but live can be so different. The other question is the time. Universe exists for ca. 16 billion years (but no one really knows it). And how long does the human exist? - Ca. 3 million years. So maybe we just were too late or too early for other species. Or we just don't recognize them because our evolution is far behind the others. Also some scientists found that there could be 6 other demensions that we can't perceive. We know height, lenght, depht and time. So what if there are species who can't perceive these demensions? That all is hard to imagine and I know that all is hard at the edge of science but these days things change very fast. What would you've said if you had lived 100 years ago and someone would have told you that in the 90's you can talk to somebody from everywhere no matter how far you're away and no matter where you are at the moment? This little invention now known cell phone would have been a miracle.
Ok, now as you all will call me crazy I gotta say that these are just some thoughts of someone who's always trying to find the truth (ok, not always but often)