In additon to being the most in demand session drummer of all time (check out the SG discography here: http://www.drstevegadd.com/discography.htm
), Steve Gadd is also the most imitated drummer of all time, maybe with the exception of Buddy Rich. Further, Steve Gadd has had more influence on the art of drumming than any other drummer, ever, maybe with the exception of Buddy Rich and Gene Krupa.
Frankly, anyone who doesn't recongnize the genius of Steve Gadd is either just not listening, or is not able to hear.
PS: My favorite SG groove is from Chuck E's in love by Rickie Lee Jones. That groove will pull your heart right out of your chest.