I don't really go out of my way to listen to stuff that Motown put out so I can't make song recommendations, but artists like Marvin Gaye, The Four Tops, Jackson 5, The Isley Brothers, Diana Ross, Stevie Wonder, Smokey Robinson, The Temptations, etc.
If you want a more unpolished sound (like what you get from Stax) then maybe try Otis Redding, Isaac Hayes, Sam & Dave, Billie Holiday, and Booker T.
Straying away from the Motown dealio, Sam Cooke and Nina Simone, just 'cause I'm a big fan of them haha. They are more of a mixture of R&B/soul and sometimes jazz on Nina's part.