I think in brief, one has to be clear whether we are talking about life, or intelligent life, and whether we are talking about the Solar System, the Galaxy or the Universe.
I suspect that microbial life is quite common, even possibly occuring elsewhere in our Solar System - something I discuss briefly in one of my hubs. This is because the basic chemical building blocks of life, and the other necessary requirements - such as water and heat, seem reasonably common, and - once given the chance - life did evolve quite quickly here on Earth.
Intelligent life is a bit different however. It probably exists somewhere else in the Universe, but I strongly suspect there is no other intelligent life in our Galaxy. No space in a short answer to explain why, but basically I suspect any intelligence which is even just a few million years in advance of us (nothing in terms of the age of the Galaxy) would by now have colonised the entire Galaxy, and would have visited us; (and I don't believe they have!) I hope to write a hub about it one day.