Two issues here. First, you've ignored the astronomical amount of computational resources required to evolve an intelligence from scratch and the minimum size of a viable intelligence, which each rule out the possibility of computer viruses or genetic algorithms becoming intelligent on their own. Second, you seem to have jumped from "evolution is the only thing that can create intelligence in a universe that lacks intelligence" to "evolution is the only thing that could make computers intelligent", ignoring the pre-existing human intelligence that could bypass the whole evolution bit.
3rd May 2014: I no longer hold the ideas in this article. IsaacLewis2013 had fallen into something of an affective death spiral around 'evolution' and self-organising systems. That said, I do still hold with my statement at the time that this is 'as one interesting framework for viewing such topics'.
I've recently been reading up on some of the old ideas from cybernetics and self-organisation, in particular Miller's Living Systems theory, and writing up my thoughts on my blog.
My latest article might be of interest to LessWrongers - I write about the relationship between life, purpose, and intelligence.
My thesis is basically: