Didn't read all the responses, so I'm not sure if someone said this, but it's not a matter of IF other intelligent life exists elsewhere in the universe. It's a matter of when.
We could detect light reaching us that tells of a civilization far more advanced than we are, yet that civilization was annihilated millions of years ago.
When you get into the billions of light years and the size of the universe and the age of the universe, we're really just not able, as humans, to conceive of these types of things.
For the record, I believe other intelligent life exists elsewhere, and I believe they have visited and are visiting us.