depends on the question..
The universe is so incredibly large and we discover new exoplanets daily on average
(1500 or so in 2016 alone which helps with the average

)
and that's only our home galaxy of course...
with millions of galaxies, those numbers grow incredibly large incredibly fast..
even the tiniest non zero chance for life to form on a planet
(and the fact that it did on our planet makes it a non zero chance)
means there must be life on different planets as well somewhere.
maybe even intelligent life
So
Do I believe in non terrestial life, for sure I do;
Do I believe in extraterrestial INTELLIGENCE, I'd still say yes though my inner certainty level dropped!
Do I believe the aliens were, are or -anytime soon- will be on earth?
I have
serious doubts let's say.
Distances in our galaxy alone are so enormously big that even lightspeed as the universal speed limit is a sincere obstacle for travelling the universe.
We can't figure out Warp drives yet (at least not physically)
And with what we know so far we'd need to prepare a track first to even make it possible.
(not to mention we lack the power to do so)
Anywhoo.. I doubt our planet has anything to offer that'd peak any hyperintelligent species' interest that's smart enough to figure those things out.
So yeah.. Aliens...
indeed one of my favourites...
'sid