as said above, given the unimaginable size of the universe it is basically impossible that there is not other intelligent life out there. basically mathematically impossible for there not to be. IMHO, that isn't really a question.
the real question is (AGAIN considering the unimaginable size of the universe - e.g., multiple million/billion light years between galaxies, etc) have any of them discovered the ability to actually get to us.
but, then, considering the age of the universe, it is possible that there is intelligent life that is MILLIONS, if not BILLIONS, of years more advanced than us technologically. just think of how much more technologically advanced we are in the last 100 years, so just imagine how much more technologically advanced the human race would be in 1 MILLION years!!!!! (granted, we will never get there before destroying ourselves/ each other....but that is another topic entirely)