When I was a freshman at college, I took a course of international economics. The lecturer introduced one econ textbook to the students. That was the Samuelson's economics. Of course, it was the one written with Nordhaus and soon I dropped from this course because I felt it was enough to read it.
I can't talk about Samuelson and his work because I don't know what he really did in economics. However, he is so famous in the area of economics that most of people should find his name in any introductory econ textbook.
Of course, Japanese economists of older generation studied economics with his textbook and if they were asked who wrote a great econ text, they would definitely answer "it's Samuelson". He is certainly a brand name in Japan too and influenced them so greatly. Unfortunately, I have never read his economics (I've read Mankiw's one instead.) but I heard most of econ textbooks have followed his style of economics by introducing micro, and then macroeconomics.
Recently, I have been wondering what's the true meaning of the distinction between micro and macroecon. Well, I think it's easier for econ teachers to teach beginners economics. But as an econ beginner I struggled to understand what econ is like; Micro seems very different from macro in intro econ textbooks. To be precise, Keynes theory(AD-AS analysis) seems different from New Classical one(Demand-supply diagram).
I know Barro of Harvard tried to integrate them into one. I am not somewhat happy with the Barro's style of economics and I cannot give alternative version of econ(it's really a big task!), but I would say there's no more need than to make the distinction.
I would say macroeconomics should be described as an applied microeconomics and this trend has been already accepted. Why have many of intro econ textbooks still followed an old-fashioned Samuelson's style of econ text? It might be a stable equilibrium of econ style.