Who is the greatest mathematician? Graduate students in mathematics will argue about this forever, but the nominees certainly include Euclid (Egypt, b. ca. 325 BC); Archimedes (Greece, b. ca. 287 BC); Rene Descartes (France, b. 1596); Pierre de Fermat (France, b. 1601); Blaise Pascal (France, b. 1623); Isaac Newton (England, b. 1642); Gottfried Wilhelm Leibniz (Germany, b. 1646); Leonhard Euler (Switzerland, b. 1707); Karl Friedrich Gauss (Germany, b. 1777); Evariste Galois (France, b. 1811); Bernard Riemann (Germany, b. 1826); Jules Henry Poincare (France, b. 1854); and David Hilbert (Prussia, b. 1862).
This list excludes logicians such as Georg Cantor (Russia, b. 1845) and Kurt Gödel (Austria, b. 1906). Mathematicians and logicians are forever arguing about whether the former is a branch of the latter or vice versa. If logic is considered mathematics, then these two are certainly contenders.