Ultimately, this is more than just a random phrase that people throw about. It is an issue that science can actually speak to. Since discussions of evolution focus so much on competition, it makes sense to take a look at the latter — cooperation. And an analysis of this reveals that nearly every major revolution in evolution is the result of cooperation. Get a breakdown of the science behind the myth that "nice people always finish last" in this AsapScience video, which is based on Richard Dawkins The Selfish Gene
And if you want more information, but don't want to wait to read Dawkins' book, see this article on the topic.