"foolishness. theirs no such the as greatest. everyone always contributes there own to the world no one is ever better then anyone eles. for we are all equal." Wrong. Hitler and Einstein were not equal. We are not equal. We are all different.
Nietzsche is great for his spirit and the range of his thought, though I disagree with him often. Emerson has many of the same ideas, but without the misogyny. I'm actually quite the fan of Heidegger's ideas, even if they are a bit overbearing; same goes for Sartre. It also bothers me when any philosopher cannot reconcile metaphysics and modern science. As far as Classical thought is concerned, Lucretius, all the way, with a deep bow to Heraclitus. On the other side of the globe, quite a number of Zen teachers tickle my fancy. Particularly, Zhaozhou (Joshu), Linji (Rinzai), Huangbo, and Eihei Dogen. The Tao Te Ching goes without saying.
To say who is the greatest philosopher requires some defining of what 'philosophy' is If by philosophy you mean someones ability to most accurately describe the nature of the mystery of being, then I would say Lao Tzu. I consider the tao te ching to be the most accurate words to make it to english particlarly this specific translation http://academic.brooklyn.cuny.edu/core9/phalsall/texts/taote-v3.html although some things are still kinda screwy in the translation However I like to think of the philosopher more like a critic of society. Someone who keeps tabs on, and attempts to keep in check the absurdities of his culture. By this, the term philosopher to me implies a certain amount of 'here and now'. By this meaning I would say Terence Mckenna. The book True Hallucinations I consider the magnum opus of modern psychedellia
When he was on DMT. I agree though that Terrence Mckenna was a great philosopher, he was so brilliant, I could just listen to him talk for hours.
A very intresting short biography of Terrence Mckenna. http://rotten.com/library/bio/mad-science/terence-mckenna/
Philsophy is a fun subject, there were probably incredible philosophers that were lost to the pages of history because of the burning of the library of Alexandria. It's interesting to think about where we would be now had the library not been destroyed. The combined works of all the greatest minds of the classical age were burnt to the ground, only a few of their manuscripts were recovered, it's really sad to think about. Eratosthenes is one philsopher that probably was greater than most, but only a few pages of his scrolls were found, what a waste! Astronomers and philosophers say that if the library had not been destroyed, our civilization would be at least twice as advanced as it is today. But to be a little more on subject, I'm really partial to Carl Sagan. He was an astronomer first, but I think he was also somewhat of a philosopher. But other than that, I'd say I really like my own philosophy of life quite a bit. Your own philosophy on life is the only one that really matters anyways!