Arthur C. Clark, sci-fi writer, inventor, discoverer, etc, once said, "Two possibilities exist: Either we are alone in the universe or we are not.  Both are equally terrifying."

He wrote 2001: A Space Odyssey, The Fountains of Paradise, and my favorite, Childhood's End, among other books.  He brings up an interesting point.

Which would be worse?  To be completely, utterly alone on this one little planet in the entire universe?  Or to have other alien races, good or evil or neither, out there existing.  Maybe we run into them, maybe not.  Maybe humans are more advanced, maybe not.  Or maybe there's absolutely no other life.

What are everyone's thoughts?

Neither of them are scarier than not knowing. You look, you find nothing, yay theres nothing there. You look and theres something, now what? At least you know. Not knowing what you're going to find is the scary thing.

Part of LDS Theology (and something I believe in) is that there are other Earths, populated with children of God like us.  Now that doesn't necessarily imply "aliens" in the way that sci-fi popularly depicts them, but it's an interesting concept.

Aliens. With laser. Or robots. Or alien robots with laser guns.

But seriously, being alone in the universe is worse for me. The idea that the universe is so vast and massive, that we are the only species on it is pretty bad. It means no matter what we do, we're useless in the end. If there was an alien species out there, they could learn from us, the same way we learn from history. But if we're alone, when we die out, the universe will be a barren wasteland.
Or worse, we'll reach the end of the universe without anything to show for it. Alone. and forgotten.

With a universe so vast, I doubt that we are alone. However with the present state of technology there is no way we can make contact with them, and I think it's fine. Because if there ARE aliens elsewhere and they see how weak we are as a species - killing each other for reasons other than self-defense - then we are done for. If they can come here then their technology would be far superior and they can wipe us out while we discuss the Kardashians' latest publicity stunt.

Let me start, by saying we are not alone. There may exist aliens in our own galaxy, let alone universe.

As for the hypothetical of what is scarier, I would presume us "being alone" to be the scarier option.

My way of thinking is thus, given what we do and can know about intelligent life in the universe: Any intelligent life form is going to have the capacity to wonder the same things we wonder. We may not be able to properly communicate, but our own fears and preconceptions are the same in the inverse. Just as we may fear life outside our galaxy, so too, may life outside our galaxy fear us.

If we opt to not fear, then odds are, they will have come to the same rationalization.

This of course, is just heresay, based on how human beings interact. Just as it is likely life forms like us exist, it is also possible that life-forms like us do not. But since we cannot assume one way or another, it is best to go off what we know.

We know that we exist, so we should prepare for the probability that there are others like us (in the traditional sense, an alien) out there. It makes no sense to fear them unless we fear ourselves.

It would be scarier to be alone, because no amount of exploration would satisfy us. Just as exploration is about finding new worlds and seeing new sights, it is also about connecting with life, and finding companionship.

To be alone in the void of space would be nothing short of disappointing.

I like the idea of thinking there are aliens out there that we can learn from. I'd hate to think we are as far as "evolution" or the universe went. I'd love to think in 20 years we will be able to travel to other galaxies and live among other species more advanced. That would be great.

I see a lot of people are making the argument that being alone is scarier, but while that is a nice thought, the idea of life that operates entirely different from us is just naturally terrifying. If we were to encounter an alien that worked on an entirely different logic than us, we would never be able to communicate with it, because we would never be able to understand the actions of each other. Does this mean that alien life would automatically be dangerous? No. But it does mean that alien life is undeniable scary.

The more we have in the universe, we begin to be less and less certain of things. I like being certain, it makes me feel powerful.

Having nothing else in the entire universe wouldn't bother me as much as having things would. I like sticking to things I can understand.

And I can understand a lot of things because they've already been researched extensively over time and have the information compiled in various encyclopedias.

If they did exist, I wouldn't be scared of it though. I could care less if they're friendly, if they're genocidal, it really doesn't matter. They probably aren't interesting and there's no use studying the habitat if it doesn't apply to what we know as our world.

neither, humans are among the scariest things ever, easily.

Aliens. We would not be able to compete with them nor would we be able to cooperate long enough to fight them.

I find neither terrifying, but one certainly more exciting than the other.

Well I don't know what to say but hey its every ones opinion is it but if you ask me I say does it matter because what if these aliens are super nice but I guess we will never know but right now its fine to me.but hey its whatever floats your boat

Why does everyone assume the aliens are more advanced than us? Maybe they're stuck in the stone age because there is no iron on their surface?

No Aliens. The rest of the universe being empty, It's kind of a depressing and outright disappointing thought, though granted it would make us seem more special. Humans are scary on their own. Though I find no alien life existing very unlikely. Even so it's not a certainty that alien life would be more advanced than us, in the likely event that it does exist there probably is but there are probably just as many less developed life forms.

Other than reasons already stated, I think the idea of no alien life in the universe is the scarier thought because it takes away any goals we could have as a species. I think, to some extent, being able to communicate with another world would bring some more peace to our world. When we're alone, there's nothing to stop humans from tearing each other apart. But when there's something else out there, perhaps it would be more easily seen that the wars we fight are civil. I'm not advocating a war with aliens, especially since I hate how most sci-fi alien encounters assume there MUST be a war, but having other life outside of the Earth would help people realize that we are one species. Perhaps it would take away some racism and discrimination in the world. We could finally all be humans instead of black, white, etc. 

Zlinqx : that'd make us seem special, huh? the phrase " if everyone is special then no one is special" comes to mind since we'd be everyone in that case.

For myself, I think being alone is more scary. If the universe is billions of years old, and truly "infinite," it would be disturbing that we were the only living species to develop intelligence. I highly doubt that is the case looking at sheer probability, but it could be the case. The unknown is what causes fear in most, so discovering alien life may be more terrifying when it actually becomes our reality. The possibilities are endless for what type of race or species we may come across, so it kind of depends on what we find, and how capable we are at communicating with them when the time comes.

A theory I like to live by is that the universe is infinite. Infinite in the sense of a never-ending stretch of galaxies. So if there is an endless stretch of galaxies, an "infinity," that would entail an infinite number of earth-like planets, mars-like planets, bi-solar systems, tri-solar systems, etc. The universe is indefinitely large because there is no way to prove the universe has an 'end' or a 'limit'. We have been able to observe galaxies past galaxies that we would never be able to reach, even traveling at lightspeed for two billion years. So yes I find it highly probable that earth-like planets carrying human-like species exist. That being said, humans on earth are already limited due to our war, politics, religion, and we can only assume that any other species would be the same. There is no truly 'perfect' specimen after all. And to add on to that, we would have to imagine the sheer amount of time it will take for our race alone to progress technologically to the point of traveling throughout our own galaxy. Hell, we are just this moment finally getting around to traveling to mars. We should have been on mars a decade ago but the 'terrorism' threat and imminent war has prevented our progress because as I have stated, no species is 'truly' perfect. So all that being said, we will not know anything of the outer galaxy alone for thousands of generations to come. Humanity is climbing closer to a man-made apocalypse each day due to our laziness and our progression into the depths of wasting resources. We are expected to reach a man-made apocalypse by 2050. We are expected to go extinct as a species by 2120 if we do not change our ways rapidly. However, contrary to this scenario, the dinosaurs going extinct allowed humanity to bloom and flourish. So potentially, the extinction of the human race could pave the way for a new species (potentially more intelligent) to build upon our failure.

This is merely speculation, but scientific research says that our consumption of resources on earth will bring us to sudden extinction around 2120. That is more scary to me than anything else. And I can only this has happened, is happening, or will happen to any other alien planets that exist out there.

To me, being alone is pretty much the scariest thing ever for me. There has to be something out there, because I don't want our planet to be the only one to support life.