Teddy Pendergrass joined Harold Melvin and the Blue Notes as the drummer and became the lead singer. That needs to be mentioned.
But ack then, Bobby was better without NE and NE were better without Bobby and with Johnny. When Bobby was in the group initially, Mr. Telephone Man, Jealous Girl, and Hide and Seek were his standouts, but it was all bubble gum music. When he left, he made King of Stage, which biggest hit was another bubble gum song, Girlfriend. When NE and Bobby both started making more adult sounding music (the producers allowed them to grow up), they came with the heat (Don't Be Cruel and Heartbreak).
Now, they all tour together as Bobby is a shell of himself and doesn't seem like he can carry a whole show. So he needs the other guys to help him out and the other guys need him for brand/name recognition because the fans want to see all 6 (and the bag is bigger).
Also, RALPH has always been the most important member of New Edition. Ironically, he is the one whose solo career didn't pop off, but he's still the man in that group. There is no New Edition then or now without Ralph, just an RBRM.