It's worth noting within the random chance theory; we don't know how many trillions of times the universe was 'created'. It's quite possible there are an infinite number of either parallel universes or even (more unlikely AFAIK) sequential universes. Within that context, life is not improbable - it's inevitable.
If you decide to equate the formation of life to God (or aliens, etc), you're not answering the question - you're shifting it. What are the odds of a divine omnipotence manifesting itself? Certainly, it's no more likely than an infinite number of realities - chances for life to arise on earth.
The origins of life - the scientific theory - is still being investigated. Life can be said to derive from proteins, formed from amino acids; DNA defines the amino acid building blcks for proteins. It's a massively complex scenario - particularly when you include the other requisites, like membranes to contain the whole morass. The arguement used against 'chance' is that these can't just arise by random at once (the analogy is that of a tornado hitting a junkyard and assembling a 747).
The thing is, the theory doesn't say that - they evolved. One or 2 amino acids bump together, and combine. And then bumped into another cluster, so on - and eventually we end up with 'modern' proteins thousands of amino acids long. This type of inherent complexity is seen all the time in nature; the formation of polymers, crystallization, sugars assembling into starches. Neither is life, of course, but it proves that natural 'assembly' and complexity occurs.
Life - all life, at least on this planet - itself only requires 4 basic elements (carbon, hydrogen, oxygen and nitrogen), combined with a few trace others.
There are things that are unquestionably odd about the arisal of life on Earth - like how (pre atmosphere) UV rays didn't break up the molecular bonds on early life, or how monomers weren't polymerised if life evolved in water. This doesn't mean the theory is untenable. It just means we still are exploring it.
They do, incidentally have evidence of life from 3.85 billion years ago, in marine sediment from Akilia Island (in Greenland). Although it's obviously not fossilized, you can detect the trace telltale residues from once-living organizms - carbon isotopes and phosphates.
It's easy to pick an answer that can justify itself - by invoking the God answer you don't need to even consider the question. Why does my Pc work? Is it because God powers it? Why not?