Man, you know about Gravediggaz? Good shit bro. They're pretty good, rather morbid, but good to listen to nonetheless. But better than Biggie? Probably not, even though I'm not much of a fan of Biggie.
Personally I like Eminem, one of my favorite artists in history. He's the one who really got me into rap back in the day, plus he's from Detroit (where my entire family is from), so I can't help but love him. He's not as good as Rakim or Nas, but he's just under that level and still damn good.