I would add Ghandi; Einstein; Bill Gates; and Steve Jobs to your list.
Ghandi, because he taught the world that peace is a lifestyle not merely something we talk about.
Einstein, because his work in mathematics literally changed the way our scientists perceive the universe.
Gates & Jobs because their work in computing made our modern world possible.

Speaking of Mandella, he would be the first to tell you that death is a natural, and unavoidable, part of the life cycle.
Life should be revered and lived well. You should strive to leave the world a better place, so that when you pass others will not mourn but rather celebrate the love and lessons you brought them.