I would agree with the sentiments of Churchill being an important figure at least in the first half of the century. He also set the tone of what world relations would be for the second half.
I think the Reagan statements are interesting. Especially given the context of the reasoning. Reaganomics sucked really bad for a lot of people. It was on his watch that the slippery slope started with outsourcing millions of jobs. The rich got richer though.
As for me, I have a few I will throw out there. Ghandi is certainly worth mentioning. Mao would be another. Mentioning Mao would cause me to throw out other names like Lenin, David Ben-Gurion, Martin Luther King. Then also depending on the context one wants to argue, something could be said for Niel Armstrong, Henry Ford, and whoever invented the internet...
Personally, I am going to lean in a direction that looks at how the 20th century will be viewed in 500 years. Humanity made some very signifigant changes in the time period from 1900-2000. So I am going to nominate a set of brothers from Ohio who by trade were bicycle mechanics. In 1903 with little fan fair they developed the first viable way to simply control a heavier than air machine in flight. So I nominate the Wright Brothers.
The opening of the airways to travel has changed human life like no invention since the wheel.
As a side note, there are quite a few worthy of mentioning in terms of scientific/medical advances, Fleming would be one, and so would the folks who figured out small pox.