And I agree with Britexpat when he said "it is not necessarily about Muslims. It is more to do with countries who value the lives of their citizens more"
Another factor that made the Boston tragedy so talked about is the unexpectedness of the whole thing. I mean look at it in this way..when a news bulletin carries a story on children being kidnapped and killed brutally anywhere in the world(east or west), we may feel pain and sadness, but it has also become so commonplace around the world, that we are no more shocked by such crimes. The Boston explosion however was truly unforeseen and bizarre in that aspect.
Another similar incident could be the Villagio fire or the killing of the American teacher in Doha. Sure the dead maybe fewer in numbers than other atrocities around the world, but the very fact that it was still so unexpected and out of the blue, made these adversities much broadcasted and talked about for days to come.