He was LA's version of Brett Hull, a good modern day comparison would be Jeff Carter, but Nicholls wasn't as fast of a skater.
He was a sniper with a very accurate shot and could also get feisty as well. What made him so beloved in LA was that he really enjoyed scoring goals and he showed that with his "pumpernickel" celebration.
Was he as good as his stats suggest? Yes, definitely. Even before he exploded with 70 goals in Gretzky's first season here, Bernie was a very productive, 90+ point producing center. Although they got some great pieces in return for him in Sandstrom and Granato, the Kings dearly missed having a second line center like him behind Gretzky after he was dealt. They were never able to replace him.
After Nicholls was dealt to New York, the Kings had the likes of Todd Elik, Bob Kudelski, Jari Kurri, Jimmy Carson, Shawn McEachern and Dan Quinn all try to fill that spot behind Gretzky, but they just couldn't find a replacement for him.
Here's some video of Bernie that might give you an idea of how beloved he was as a King.