When one tries to estimate the number of planets that are in the Universe, we will find they are beyond count. Let's say if only 10% are inhabitable, they could still be millions of them that could support life of some form. Depending on how advanced they are in the realm of space travel, how many of these alien races have visited us over the last few millennia? Also, how do they get here? If they come by space craft, I would ask about the effect of travelling light years on their craft and their physical bodies. Or would they travel by stargate or similar apparatus?
Then it could be asked what is the purpose of contacting us? It might be commerce, trade, war, social or any number of reasons. If their temperaments are anything like ours, it would cover a broad enough spectrum. They may come in the name of living in harmony and passing along spiritual enlightenment, which would be great. But if they come to wage war with advanced technology better than what we have, I'd hate to see what would or could happen.
Keeping an eye on what is entering our air space is a wise thing to do. Since we probably can't trust what the professionals are telling us on what is really happening, the general public will have to develop other ways of contacting visitors from other planets. I am at a loss on making any suggestions here on how to do this. While I can understand the desire to contact alien life forms, is it safe enough to do so until we know who or what we are dealing with? It would be like inviting someone into your home without knowing who they are.
To say we are the only inhabited planet in the entire universe is pretty egotistical on our part. We just may find ourselves on the lower half of the intelligence scale considering how we treat ourselves, each other and what we are doing to our planet.
When and if we do make contact with an alien race, we may have to realize that we many not be dealing with a species as we know it here on Earth. They might have completely different mental or physical characteristics or needs than what we do. We have to be clear on who or what we're dealing with as movies and TV shows are out to make the big bucks not to present a realistic view of what is actually going on.
Maybe some of the alien contacts will be beneficial and connect us with a greater universal community. When and if contact with aliens becomes a reality, we need to proceed with great care and caution if we wish to continue our existence.