1. Descartes’ is not just the author of the meditations; he has historically significant physics, and arguably anticipates the second law of motion
2. Descartes’ has interesting, but not terribly significant mathematical innovations, still, that mapping system and developments in trigonometry is pretty significant, right? Even if it’s not metaphysics…
3. Descartes’ represents a philosophical moment; when freethinking was opposed and atheism was a stigma. There is at least one commentator out there who argued that Descartes was an atheist…(that’s a very complicated story though…)
4. Descartes’ arries on the spirit of Aristotle to systematise reality; the project Descartes had of Le Monde was a promising idea. Philosophers today are hardly as ambitious as he was, not even Kant had the pretentions of Descartes. Perhaps the only people who have similar pretensions are rationalist theologians and theoretcal physicists who talk about the “theory of everything”.
5. Spinoza’s axiomatic system in the Ethics was predated by Descartes (Principles, III)
P.S. A comment about dualism, scepticism and the ontological argument for God are purposely omitted; they are hardly significant compared to the above.