Seeds of Life
If we exclude the belief in divine creation*, that is an utterly fascinating question with huge implications - whatever the answer.
According to some views, life may have been initiated by aminoacids and other organic molecules that formed in space and were carried to our planet by comets and asteroids - despite the high-energy impacts, there are definite chances that a relevant fraction of these molecules can survive. And then (this is in great part my own view) the compounds thus arrived would act as sort of templates, directing the subsequent developments of chemical systems on Earth. And starting the long, hard slog of life and then evolution. The template effect isn't so peregrine from the standpoint of supramolecular chemistry and catalysis.
In other words, there would be seeds of life out in the deep space, which will start organic life if they reach a suitable planet (or another body, eventually).
Now, the composition of interstellar dust clouds, as far as I know, does not change much from one point to the other of our galaxy at least. This has an interesting implication: all life in the Milky Way at least may very well be based not only on carbon, but also on very similar building blocks - aminoacids. There is still room for a huge deal of variation, but all living things in this case would share a good deal of basic biochemistry.
Another interesting question is, what does influence the development of these seeds? Is it more a matter of local conditions, or their inherent properties? If the latter influence is dominant, all life may be not too dissimilar from the Earthly version.
However, there is no way to tell unless we either find genuine xenotic organism - or create some new lifeform from scratch. Either way, it is a mess. The confirmation that macroscopic xenotic organisms do exist would cause a huge cultural shock in theists and atheists alike; while the creation of new life from scratch poses serious ethical questions.
But boy, this stuff keep the wheels in my head spinning!
* Creation is not so fascinating for me because once it is said "God wanted thus for His own inscrutable reasons", the debate is pretty much over.