The statement that for the vast majority of time there has been no life on Earth is incorrect. Scientific evidence shows that life has existed on the planet for at least half of its existence in single-cell form, and perhaps up to three quarters of Earth's history or more.Look at it this way - throughout the billion-year life time of the planet Earth, the vast, vast majority of time there has been no life at all and it is a miniscule proportion of that time that humans have been around to be consciously aware of any alien visitors or communications and even now, only in a limited manner. Even if a particular planet is capable of generating and supporting life, it's still a massive long short to catch it at any meaningful point.
In short, single-cell organisms in some pool of liquid out there, probably. Little green men in flying saucers, probably not.
So, life seems to have developed fairly quickly on Earth once the chaos settled from the first billion or so years, and the result is that Earth has had life for the majority of its existence.
Then, based on results from the Kepler space telescope, there statistically should be billions of planets similar to Earth in our galaxy, and then current estimates from NASA suggest that the number of galaxies in the universe at least number in the hundreds of billions, which means there are probably more galaxies in the universe than there are stars in our galaxy.
I'd go with the safe vote, that a lot of lifeforms probably exist out there. I haven't seen convincing evidence that anything has visited Earth yet, though.