There are an infinite number of planets with life - the problem is the distance from us.

Have we ever been visited by aliens? - maybe, hard to say

Even though it makes sense that we are not alone, I think we sometimes fail to recognize just how rare our situation is.

Not only is Earth in the right place, it has remained in the right place for billions of years. Not only do we have an atmosphere, but that atmosphere has been relatively consistent for billions of years, continuously mixed and stirred by an active weather system that is in part maintained by the Earth's magnetic field.

So, yeah, we are probably not alone, but there probably aren't very many planets with this combination of exceptional good luck.

So to paraphrase the great Enrico Fermi, "where the hell are they all?"

Its the only place where we know life exists. That said, the volume in which we've searched for life was reported to be a sphere of radius about 300 light years (LY). Our galaxy is and oblate spheroid with an axis of the order of 100,000 LY. Lots of searching left to do in the Milky Way.

There are purported counts yielding 140 billion galaxies in the universe. Most likely we'll never know if any of them hold life.

The operative word here is, "if"! The odds that we will ever be able to span those distances are, pardon the pun, astronomical. Plus there's the issue of how we travel. We can send robots, who don't need oxygen, food, light, and can go on for generations as long as they need to. Biologically, at least as we are right now, we can't do it.

I'm hopeful that it "could" happen, but I suspect we're far more likely to cause ourselves to go extinct before that happens. Which, by the way, if we could travel the galaxies, we might come upon several other species who have eradicated themselves on their way to a technological society.