Population is certainly a measure of success for a species, however it is not a particularly good one in my opinion.
China's population boom occurred during one of its least successful times in history. China's current success comes at a time of minimal population growth. What's more "successful"? A prosperous society with a static population, or a starving one with a rapidly growing population?
Was China of 1970 more successful than Europe of 1450? It had more people...
Plus, I think terms of "success" with respect to a /nation/ is slightly skewed when compared to the "success" of genetics or species. I don't think that is an accurate cross-comparison.
Given all those things being equal, certainly a higher population would be more successful. However fast population growth is likely to work against most of those goals.
Could you explain why the explosion of human population in the last several thousand years (http://en.wikipedia.org/wiki/File:Population_curve.svg) is possible, and why it does not imply success? Particularly with the limited resources we've overcome with the advent of crop rotation, agriculture and farming, technology, etc. - and the limited resources today we are still solving for and continually will do so?
It looks like we need a criterion for "success" and "evolution" and "progress"! I would love to hear your input.