According to me, he is one of the most underhyped persons in the industry. Everything from Linux, iOS (objective C), other OS, programming languages like C++, Java, C#(Extensively used by Microsoft) were inspired by C.
His two contributions (C and UNIX) are easily two of the most important in the history of computers, and if you are a programmer or a techie, you cannot describe in words how valuable his contribution to the industry, or even mankind has been.
He can be rightly called the father of the software industry. RIP Dennis Ritchie.