While Simpsons, in its prime, practically revolutionized the genre of dramatic cartoons, keep in mind that the writers of Futurama were of the same bunch.
That said, for me, The simpsons has no equal, in its prime, as it pioneered realistic character traits unlike anythign I had ever seen.
Humanistic characters such as Krusty the alcoholic and smoking clown, Moe the bitter bartender, Mr. Burns the belligerent and yet childlike emperor of the town, and Homer, the homely idiot with undying love for his family, have made me biased.
I had never seen such rich, such developed, such truely viral and realistic portrayals of humanity, that even after lauding Groening incredibly entertaining and absolutely brillaint "futurama," I can help but fall back on the memories of the cartoon show that helped shape my mind.
Futurama is excellent, practically genius, but the simpsons is the undisputed king of the philosophical dramatic comedy.