Of course, there is no denying that Newton built upon much of the work of his predecessors - notably Galileo's early experiments in motion, as well Kepler, Huyg

Of course, there is no denying that Newton built upon much of the work of his predecessors - notably Galileo's early experiments in motion, as well Kepler, Huygens, Barrow and others. But there were a significant number of original ideas, research, analysis, and experiments that added to, refined and extended their work, and most importantly formalized it all into a coherent, unified corpus in the form of the Principia. And that work was done single-handedly, all by himself, working alone, and is considered seminal in laying the foundations of science for the next three hundred years. To call it just a grand synthesis, severely discounts the magnitude and impact of that achievement.