Contemporary black gospel has always been influenced by other contemporary styles of black music (funk, r&b, hip-hop). As with contemporary Chrstian music (CCM), the genre is defined soley by its lyrical content rathern the the format. So weather it is blues, jazz, r&b, or rock really doesn't matter. It's all about the message of the music. Now your friend does make some good points. Worship leaders, musicians, and singers need to be lead by the Holy Spirit to attain the right balance of song selections. Music is a very complex artform that has elements of entertainment as well as ministry deeply interwoven together. With regards to musical style, I think that many people will agrere that tradional black gospel, older choir music, and even early contemporary gospel had a unique feel. They may have been influenced by other styles like the blues, but there was something unique about them.