I believe there is a high probability that somewhere out in the seemingly infinite universe, there must be other forms of life.
Whether that's like little alien cells, or tiny animals, I don't know.
Could possibly be space-faring sentient life-forms, but chances are they'd be so unbelievably far away from us that they'd never get word of us from our broadcasts into space or our space probes.
And if they did, it'd take them so long to travel to Earth that by the time they got here, we might not even be here.
And if they did turn up now, then they'd probably have had to have seen our planet millions if not billions of years ago, when it was little more than volcanic mess. Which begs the question, why travel here in the first place?
So, I believe that there is likely some life out there, but I don't think they'll be visiting anytime soon, nor that they have visited.