Given the size of the universe, and the time span it's existed over (and will exist over), it seems pretty much inevitable to me that there'd be alien life out there somewhere at some point besides that which has developed here on Earth.
However, given the size of the universe, and the time span it's existed over (and will exist over), it seems to me that "incredibly unlikely" doesn't even begin to convey just how unlikely it would be that such life would exist, be spacefaring, and have found and travelled to Earth during the ridiculously brief period humans have been around.