You forgot to mention Turing :)
Turing doesnt get much space in school textbooks.
And von Neumann too despite being one of the giants of mathematics in 20th century.
Wow, my list really should have included von Neumann, perhaps the most underrated intellect of the 20th century. He'd be on a lot of people's top-n list even for n <= 3, and yet he's barely known outside of the technical world.
