Curtis, Donny, Marvin, Sly Stone all have immeasurable contribution to genre. I voted for Marvin , because his albums of 70's era were the greatest and most influential works of black artist ever. What's Going On had impact on rock, hip-hop, soul music, I Want You spawned Quiet Storm, Hear,My Dear and Let's Get It On influented generations of new day neo-soul artists. Damn, these were the times.