Michelle Obama said with tears in her speech, "Success isn't about how much money you make. It's about the difference you make in people's life." Logically, I think there is something wrong here.
First of all, some differences are good, and some differences are bad. Yes, Obama and his government have made many differences in many places in this planet and in many people's lives. Not every difference made is good. At least we should say "It's about the GOOD difference you make in people's life".
Is a difference good or not? The answer is of course subjective. There is no universal ground truth. It depends on whom you ask and how you ask. That is exactly why we need politicians to deliberate data from different perspectives. That is the major part of the candidates' job.
Does everyone's life need a difference? The leader cross Pacific Ocean said, "不折腾", meaning "don't sway, keep the predefined direction". In the last 4 years, Obama's government and Hu's government fought with each other on many cases where one party wanted to make a difference, and the other one wanted to keep the established advantage. By the way, Obama's government is not always the one that would like to make a difference.
Last, what is a difference after all? The world is evolving and differences happen all the time anyway. Our world have many different possibilities in the future, but we can only experience one of them. Then, the whole point in Michelle Obama's statement is the difference the party she represents wants to see. Is that subjective after all?
In no means I want to say Michelle Obama is a bad speaker. Instead, she is such a good speaker, as good as her husband, that, more often than not, too good to be a president. :-)