In terms of commercial success, Boyz II Men are the most successful R&B group of all-time, and based on what they drew from, it was easy to see why.  Coming from Philadelphia, the quartet took that soul sound, infused a bit of Detroit, but more importantly built on the New Jack Swing movement that was already popular.  The group used every portion of their vocal range (which was a lot) and they owned the 1990’s.