I imagine that life probably exists elsewhere in the universe, simply because the universe is so incredibly large, and growing evidence suggests that our planet is not especially unique. Just in the last 30 years hundreds of exoplanets have been identified, and several of them are estimated to be very similar to Earth (in terms of size, composition, distance from their star, etc).
The difficulty we have is knowing how to study these planets, since they're so far away that we can't observe them with any detail. In the future we might be able to get a better look at them by engineering a new type of telescope that utilizes the gravitational lensing effect generated by the Sun, but whether this would turn out to be at all workable in practice remains to be seen.
I personally think that life is probably quite rare, since there are several conditions that would need to be met in order to sustain life as we know it. Something like 70% of the stars in the universe are red dwarf stars, which tend to be so small that any planet orbiting within the 'habitable zone' (the area where liquid water could be sustained) would be tidally locked with their star. This would mean that such planets would likely be uninhabitable, as they would not only be subject to extreme temperatures, but they would also likely be incapable of retaining atmospheres or oceans due to their close proximity to coronal mass ejections causing them to evaporate away. This consideration alone, eliminates pretty much 70% of the universe's solar systems from being able to sustain life.
As for the question of intelligent life or advanced alien civilizations, I imagine that they are exceedingly rare, and probably so rare that we will never make contact with them. If you look at our own planet as a case study, it is estimated that over 5 billion species have existed on Earth throughout it's history, and so far only one of them (us) has evolved enough mentally to be able to even contemplate intelligence, let alone build a civilization or speculate about the existence of other civilizations elsewhere in the universe. Just let that sink in.
