We seem to find amino acids everywhere. It seems like once conditions exist that they can form, they DO form.
We don't have any equivalent building block which is anywhere nearly so ubiquitous.
In addition, these building blocks are reversible within 3kcal/mol. Life requires reversibility. http://wavefunction.fieldofscience.com/2008/10/unbearable-he...
We have no other building blocks with this kind of versatility. None.
So, life may not be based on DNA/RNA, but it's almost certain to be based around amino acids.