I cant imagine that in the entrie universe we are the only ones.. that would be traggic... odds are just so much agaisnt it...
however I am not sure what to think about aliens visiting our earth though...sounds much more unlikelly..
There is no reason not to believe that there are other species in the vast universe. But, what most of the alien "supporters" forget is that is is a vast universe.
How many people have so many opinions. The fact is that every person can be wrong, But everyone understands that our universe is very huge and there can be anything around us. I'm not sure about the existence of aliens, but there is something in this world.