His work and his methods drove economics into the position it is today. In terms of driving the economic method forward (and establishing “economic science”) he is the most important economist of the 20th century in my opinion.
Here are some links discussing his life and work:
This quote from Lucas is apt:
Samuelson was the Julia Child of economics, somehow teaching you the basics and giving you the feeling of becoming an insider in a complex culture all at the same time. I loved the Foundations. Like so many others in my cohort, I internalized its view that if I couldn’t formulate a problem in economic theory mathematically, I didn’t know what I was doing. I came to the position that mathematical analysis is not one of many ways of doing economic theory: It is the only way. Economic theory is mathematical analysis. Everything else is just pictures and talk